Publications by authors named "Sara L Thomas"

81 Publications

Post-vaccination HPV seroprevalence among female sexual health clinic attenders in England.

Vaccine 2021 Jul 12;39(30):4210-4218. Epub 2021 Jun 12.

Blood Safety, Hepatitis, Sexually Transmitted Infections (STI) and HIV Service, Public Health England, London, UK.

Background: The National HPV Immunisation Programme was introduced in England in September 2008 using the HPV16/18 bivalent vaccine. We conducted serological surveillance to explore vaccination coverage levels. We also conducted a case-control study to investigate a hypothesised cross-protective effect of the HPV16/18 vaccine against genital warts.

Methods: Residual serum specimens from 16 to 20 year-old women attending six specialist sexual health services (SSHS) between 2011 and 2015 in England were tested for antibodies against HPV16 and HPV18 using a virus-like particle (VLP)-based multiplex serology assay. Patients were classified as having vaccine-induced seropositivity if they were seropositive for both HPV types and either had high antibody levels for at least one HPV type, or moderately high levels for both HPV types. Differences in vaccine-induced seropositivity by patient characteristics were investigated using logistic regression. Vaccine-induced seropositivity was then compared for patients with genital warts (cases) and matched patients without (controls).

Results: Of 3,973 serum specimens collected, 3,870 (97.4%) had a valid result. The proportion of women with vaccine-induced seropositivity decreased with age (from 78.1% in 16-year-olds to 52.6% in 20-year-olds). Vaccine-induced seropositivity was lower among women born outside the UK, from more deprived areas and with a history of chlamydia diagnosis. A difference in uptake by ethnic group was also seen but this was largely confounded by differences in deprivation and country of birth. Among 537 cases and 1,515 controls, there was little evidence of a protective effect of the bivalent HPV vaccine against genital warts (adjusted odds ratio 0.93; 95% CI: 0.74-1.18).

Discussion: Vaccine-induced seropositivity in this high-risk population was in line with vaccination coverage in the general population although was lower in some at-risk sub-groups. This study does not provide evidence to support a cross-protective effect of the HPV16/18 vaccine against genital warts.
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http://dx.doi.org/10.1016/j.vaccine.2021.05.018DOI Listing
July 2021

The identification and validity of congenital malformation diagnoses in UK electronic health records: A systematic review.

Pharmacoepidemiol Drug Saf 2021 Jul 4;30(7):875-898. Epub 2021 May 4.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Purpose: To describe the methods used to identify and validate congenital malformation diagnoses recorded in UK electronic health records, and the results of validation studies.

Methods: Medline and Embase were searched for publications between 1987 and 2019 that involved identifying congenital malformations from UK electronic health records using diagnostic codes. The methods and code-lists used to identify congenital malformations, and the methods and results of validations, were examined.

Results: We retrieved 54 eligible studies; 36 identified congenital malformations from primary care data and 18 from secondary care data alone or in combination with birth and/or death records. Identification in secondary care data relied on codes from the 'Q' chapter for congenital malformations in ICD-10. In contrast, studies using primary care data frequently used additional codes outside of the 'P' chapter for congenital malformation diagnoses in Read, although the exact codes used were not always clear. Eight studies validated diagnoses identified in primary care data. The positive predictive value was highest (80%-100%) for congenital malformations overall, major malformations, and heart defects although the validity of the reference standard used was often uncertain. It was lowest for neural tube defects (71%) and developmental hip dysplasia (56%).

Conclusions: Studies identifying congenital malformations from primary care data provided limited details about the methods used. The few validation studies were limited to diagnoses recorded in primary care. Further assessments of all measures of validity in both data sources and of other malformation subgroups are needed, using robust reference standards and adhering to reporting guidelines.
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http://dx.doi.org/10.1002/pds.5251DOI Listing
July 2021

Seasonal influenza vaccination during pregnancy and the risk of major congenital malformations in live-born infants: A 2010-2016 historical cohort study.

Clin Infect Dis 2020 Jun 23. Epub 2020 Jun 23.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.

Background: Available evidence indicates that seasonal inactivated influenza vaccination during pregnancy protects both the mother and her newborn, and is safe. Nevertheless, ongoing safety assessments are important in sustaining vaccine uptake. Few studies have explored safety in relation to major congenital malformations, particularly in the first trimester when most organogenesis occurs.

Methods: Anonymised UK primary care data (the Clinical Practice Research Datalink), including a recently developed Pregnancy Register, were used to identify live-born singletons delivered between 2010 and 2016. Maternal influenza vaccination was determined using primary care records and stratified by trimester. Ascertainment of major malformations from infant primary care records was maximized by linkage to hospitalization data and death certificates. The relationship between vaccination and major malformations recorded in the year after delivery and in early childhood was then assessed using multivariable Cox regression.

Results: A total of 78,150 live-birth pregnancies were identified: 6,872 (8.8%) were vaccinated in the first trimester, 11,678 (14.9%) in the second and 12,931 (16.5%) in the third. Overall, 5,707 live-births resulted in an infant with a major malformation recorded in the year after delivery and the adjusted hazard ratio when comparing first-trimester vaccination to no vaccination was 1.06 (99%CI, 0.94-1.19; p=0.2). Results were similar for second and third-trimester vaccination and for analyses considering major malformations recorded beyond the first birthday.

Conclusions: In this large, population-based historical cohort study there was no evidence to suggest that seasonal influenza vaccine was associated with major malformations when given in the first trimester or subsequently in pregnancy.
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http://dx.doi.org/10.1093/cid/ciaa845DOI Listing
June 2020

Effectiveness of oral rotavirus vaccination in England against rotavirus-confirmed and all-cause acute gastroenteritis.

Vaccine X 2019 Apr 4;1:100005. Epub 2019 Jan 4.

Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK.

Background: The monovalent oral rotavirus vaccine Rotarix® was introduced into the UK infant immunisation programme in 2013. We estimated vaccine effectiveness (VE) in the first two years of the programme.

Methods: We used a test-negative case-control design and enhanced national surveillance data for 1869 vaccine-eligible children tested for rotavirus infection to obtain adjusted odds ratios and VE against laboratory-confirmed rotavirus infections. Linked anonymised UK primary care and hospitalisation data from the Clinical Practice Research Datalink (40,723 children) and random-effects Poisson regression were used in a cohort study to estimate VE against all-cause acute gastroenteritis (AGE) and AGE hospitalisations.

Results: VE against laboratory-confirmed infection was 69% (95% Confidence Interval: 40-84%) for one dose and 77% (95%CI: 66-85%) for two doses. Two-dose VE in children aged <12 months and ≥12 months was 85% (95%CI: 74-91%) and 54% (95%CI: 15-75%), respectively. In contrast, we found no evidence that the vaccine was effective against all-cause AGE (VE = -20%, 95%CI: -36% to -5%), or against AGE hospitalisations (VE = 35%, 95% CI: -86% to 77%).

Conclusions: In this first detailed assessment of VE of the Rotarix® vaccine in the English national programme, we show that Rotarix® was highly effective in preventing laboratory-confirmed rotavirus infection in young children. This provides reassurance about the vaccine's performance in real-life settings and gives key information for future cost-effectiveness analyses. The high VE against rotavirus-specific AGE, and the exceptionally successful implementation of the national rotavirus vaccine programme (with >90% vaccine coverage), explains the lack of VE against all-cause AGE because most AGE in the post-vaccine era would not have been due to rotavirus, although some underestimation of VE could also have occurred due to differential healthcare utilisation by vaccinated and unvaccinated infants. This highlights the importance of using specific vaccine-preventable endpoints for these scenarios.
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http://dx.doi.org/10.1016/j.jvacx.2019.100005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6668223PMC
April 2019

The risk of non-specific hospitalised infections following MMR vaccination given with and without inactivated vaccines in the second year of life. Comparative self-controlled case-series study in England.

Vaccine 2019 08 30;37(36):5211-5217. Epub 2019 Jul 30.

Immunisation and Countermeasures, Public Health England, 61 Colindale Avenue, London, UK.

Observational cohort studies in high-income settings have suggested that vaccination order may affect children's subsequent risk of a heterologous infection, with live vaccines reducing and inactivated vaccines (given on their own or with a live vaccine), increasing the risk. We used the self-controlled case-series method, which automatically controls for the individual level confounding to which such cohort studies are prone, to test this hypothesis. We compared the relative incidence (RI) of infections post-vaccination in two calendar periods in England; in Period 1 (September 2002-August 2006) live measles, mumps, rubella (MMR) vaccine was given on its own and in Period 2 (September 2006-April 2010) inactivated vaccines (7-valent pneumococcal conjugate vaccine (PCV7) and sometimes the combined Haemophilus influenzae type b/meningococcal group C vaccine (Hib-MenC)) were given concomitantly with MMR. Admissions for an infection of the upper or lower respiratory tract, gastrointestinal system or other site in children aged 11-23 months were selected from the Hospital Episode Statistics database in England and linked to child health immunisation histories. The analysis included a total of 24,144 infections in 21,067 children in Period 1 and 36,880 in 31,616 children in Period 2. The RI of admission for any infection in Period 1 was 1.00 (95% confidence interval 0.95-1.06) compared with 0.95 (95% confidence interval 0.90-1.00) in Period 2. Comparing the two periods showed no evidence of a difference in the relative incidence estimates with a ratio of RI of 0.94 (95% confidence interval 0.87-1.02), RIs within 90 days of vaccination were 0.94 (0.91-0.97) in Period 1 and 0.94 (0.91-0.97) in Period 2, consistent with a temporary healthy vaccinee effect. In conclusion, we found no evidence to support the hypothesis that there is a reduction in heterologous infections after MMR on its own or an increase after MMR given concomitantly with an inactivated vaccine.
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http://dx.doi.org/10.1016/j.vaccine.2019.07.059DOI Listing
August 2019

Methods to generate and validate a Pregnancy Register in the UK Clinical Practice Research Datalink primary care database.

Pharmacoepidemiol Drug Saf 2019 07 13;28(7):923-933. Epub 2019 Jun 13.

Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK.

Purpose: Primary care databases are increasingly used for researching pregnancy, eg, the effects of maternal drug exposures. However, ascertaining pregnancies, their timing, and outcomes in these data is challenging. While individual studies have adopted different methods, no systematic approach to characterise all pregnancies in a primary care database has yet been published. Therefore, we developed a new algorithm to establish a Pregnancy Register in the UK Clinical Practice Research Datalink (CPRD) GOLD primary care database.

Methods: We compiled over 4000 read and entity codes to identify pregnancy-related records among women aged 11 to 49 years in CPRD GOLD. Codes were categorised by the stage or outcome of pregnancy to facilitate delineation of pregnancy episodes. We constructed hierarchical rule systems to handle information from multiple sources. We assessed the validity of the Register to identify pregnancy outcomes by comparing our results to linked hospitalisation records and Office for National Statistics population rates.

Results: Our algorithm identified 5.8 million pregnancies among 2.4 million women (January 1987-February 2018). We observed close agreement with hospitalisation data regarding completeness of pregnancy outcomes (91% sensitivity for deliveries and 77% for pregnancy losses) and their timing (median 0 days difference, interquartile range 0-2 days). Miscarriage and prematurity rates were consistent with population figures, although termination and, to a lesser extent, live birth rates were underestimated in the Register.

Conclusions: The Pregnancy Register offers huge research potential because of its large size, high completeness, and availability. Further validation work is underway to enhance this data resource and identify optimal approaches for its use.
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http://dx.doi.org/10.1002/pds.4811DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6618019PMC
July 2019

Human herpesvirus infections and dementia or mild cognitive impairment: a systematic review and meta-analysis.

Sci Rep 2019 03 18;9(1):4743. Epub 2019 Mar 18.

Faculty of Epidemiology & Population Health, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, United Kingdom.

Interest is growing in the role of infectious agents in the pathogenesis of dementia, but current evidence is limited. We conducted a systematic review and meta-analysis to investigate the effect of any of eight human herpesviruses on development of dementia or mild cognitive impairment (MCI). We searched the Cochrane Library, Embase, Global Health, Medline, PsycINFO, Scopus, Web of Science, clinical trials registers and grey literature sources from inception to December 2017 for observational studies with cohort, case control or self-controlled designs, or randomised controlled trials of interventions against herpesviruses. Pooled effect estimates and 95% confidence intervals (CIs) were generated through random effects meta-analyses across studies with the same design, outcome, and virus type, method and site of measurement. We included 57 studies across various geographic settings. Past infection with herpesviruses, measured by IgG seropositivity, was generally not associated with dementia risk. A single cohort study rated moderate quality showed an association between varicella zoster virus reactivation (ophthalmic zoster) and incident dementia (HR 2.97; 95%CI, 1.89 to 4.66). Recent infection with, or reactivation of, herpes simplex virus type 1 or type 1/2 unspecified, cytomegalovirus and human herpes virus-6 measured by serum IgM, high titre IgG or clinical disease may be associated with dementia or MCI, though results were inconsistent across studies and overall evidence rated very low quality. Longitudinal population studies with robust repeated virus measurements taken sufficiently proximal to dementia onset are needed to establish whether, when and among whom herpesviruses affect dementia risk.
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http://dx.doi.org/10.1038/s41598-019-41218-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6426940PMC
March 2019

The validity of dementia diagnoses in routinely collected electronic health records in the United Kingdom: A systematic review.

Pharmacoepidemiol Drug Saf 2019 02 22;28(2):244-255. Epub 2019 Jan 22.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Purpose: The purpose of the study is to assess the validity of codes or algorithms used to identify dementia in UK electronic health record (EHR) primary care and hospitalisation databases.

Methods: Relevant studies were identified by searching the MEDLINE/EMBASE databases from inception to June 2018, hand-searching reference lists, and consulting experts. The search strategy included synonyms for "Dementia", "Europe", and "EHR". Studies were included if they validated dementia diagnoses in UK primary care or hospitalisation databases, irrespective of validation method used. The Quality Assessment for Diagnostic Accuracy Studies-2 (QUADAS-2) tool was used to assess risk of bias.

Results: From 1469 unique records, 14 relevant studies were included. Thirteen validated individual diagnoses against a reference standard, reporting high estimates of validity. Most reported only the positive predictive value (PPV), with estimates ranging between 0.09 and 1.0 and 0.62 and 0.85 in primary care and hospitalisation databases, respectively. One study performed a rate comparison, indicating good generalisability of dementia diagnoses in The Health Improvement Network (THIN) database to the UK population. Studies were of low methodological quality. As studies were not comparable, no summary validity estimates were produced.

Conclusion: While heterogenous across studies, reported validity estimates were generally high. However, the credibility of these estimates is limited by the methodological quality of studies, primarily resulting from insufficient blinding of researchers interpreting the reference test. Inadequate reporting, particularly of the specific codes validated, hindered comparison of estimates across studies. Future validation studies should make use of more robust reference tests, follow established reporting guidelines, and calculate all measures of validity.
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http://dx.doi.org/10.1002/pds.4669DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6519035PMC
February 2019

Association of herpesviruses and stroke: Systematic review and meta-analysis.

PLoS One 2018 21;13(11):e0206163. Epub 2018 Nov 21.

Faculty of Epidemiology & Population Health, LSHTM, London, United Kingdom.

Background: Herpesviruses induce a range of inflammatory effects potentially contributing to an increased risk of stroke.

Objectives: To investigate whether patients with infection, or reactivation of, human herpesviruses are at increased stroke risk, compared to those without human herpesviruses.

Data Sources: Six medical databases and grey literature sources from inception to January 2017.

Study Eligibility Criteria: Studies where the exposure was any human herpesvirus and the outcome was stroke. We included randomised controlled trials, cohort, case-control, case-crossover and self-controlled case series designs.

Methods: Meta-analyses when sufficiently homogeneous studies were available. Quality of evidence across studies was assessed.

Results: We identified 5012 publications; 41 met the eligibility criteria. Across cohort and self-controlled case series studies, there was moderate quality evidence that varicella infection in children was associated with a short-term increased stroke risk. Zoster was associated with a 1.5-fold increased stroke risk four weeks following onset (summary estimate: 1.55, 95%CI 1.46-1.65), which resolved after one year. Subgroup analyses suggested post-zoster stroke risk was greater among ophthalmic zoster patients, younger individuals and those not prescribed antivirals. Recent infection/reactivation of cytomegalovirus and herpes simplex viruses, but not past infection, was associated with increased stroke risk; however the evidence across studies was mainly derived from small, very low quality case-control studies.

Conclusions: Our review shows an increased stroke risk following zoster and suggests that recent infection or reactivation of other herpesviruses increases stroke risk, although better evidence is needed. Herpesviruses are common and potentially preventable; these findings may have implications for reducing stroke burden.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206163PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6248930PMC
April 2019

Zoster vaccination inequalities: A population based cohort study using linked data from the UK Clinical Practice Research Datalink.

PLoS One 2018 15;13(11):e0207183. Epub 2018 Nov 15.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.

Objective: To quantify inequalities in zoster vaccine uptake by determining its association with socio-demographic factors: age, gender, ethnicity, immigration status, deprivation (at Lower-layer Super Output Area-level), care home residence and living arrangements.

Method: This population-based cohort study utilised anonymised primary care electronic health records from England (Clinical Practice Research Datalink) linked to deprivation and hospitalisation data. Data from 35,333 individuals from 277 general practices in England and eligible for zoster vaccination during the two-year period (2013-2015) after vaccine introduction were analysed. Logistic regression was used to obtain adjusted odds ratios (aOR) for the association of socio-demographic factors with zoster vaccine uptake for adults aged 70 years (main target group) and adults aged 79 years (catch-up group).

Results: Amongst those eligible for vaccination, 52.4% (n = 18,499) received the vaccine. Socio-demographic factors independently associated with lower zoster vaccine uptake in multivariable analyses were: being older (catch-up group: aged 79 years) aOR = 0.89 (95% confidence interval (CI):0.85-0.93), care home residence (aOR = 0.64 (95%CI: 0.57-0.73)) and living alone (aOR = 0.85 (95%CI: 0.81-0.90)). Uptake decreased with increasing levels of deprivation (p-value for trend<0.0001; aOR most deprived versus least deprived areas = 0.69 (95%CI: 0.64-0.75)). Uptake was also lower amongst those of non-White ethnicities (for example, Black versus White ethnicity: aOR = 0.61 (95%CI: 0.49-0.75)) but was not lower among immigrants after adjusting for ethnicity. Lower uptake was also seen amongst females compared to men in the catch-up group.

Conclusions: Inequalities in zoster vaccine uptake exist in England; with lower uptake among those of non-White ethnicities, and among those living alone, in a care home and in more deprived areas. Tailored interventions to increase uptake in these social groups should assist in realising the aim of mitigating vaccination inequalities. As care home residents are also at higher risk of zoster, improving the uptake of zoster vaccination in this group will also mitigate inequalities in zoster burden.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0207183PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237346PMC
April 2019

The Impact of the National HPV Vaccination Program in England Using the Bivalent HPV Vaccine: Surveillance of Type-Specific HPV in Young Females, 2010-2016.

J Infect Dis 2018 08;218(6):911-921

HIV and STI Department, Centre for Infectious Disease Surveillance and Control, London, United Kingdom.

Background: The national human papillomavirus (HPV) immunization program was introduced in England in September 2008 using the bivalent vaccine.

Methods: We collected residual vulva-vaginal swab specimens from 16 to 24-year-old women attending for chlamydia screening between 2010 and 2016 and tested for HPV DNA. We compared changes in type-specific (vaccine and nonvaccine) HPV prevalence over time and association with vaccination coverage. For women with known vaccination status, vaccine effectiveness was estimated.

Results: HPV DNA testing was completed for 15459 specimens. Prevalence of HPV16/18 decreased between 2010/2011 and 2016 from 8.2% to 1.6% in 16-18 year olds and from 14.0% to 1.6% in 19-21 year olds. Declines were also seen for HPV31/33/45 (6.5% to 0.6% for 16-18 year olds and 8.6% to 2.6% for 19-21 year olds). Vaccine effectiveness for HPV16/18 was 82.0% (95% confidence interval [CI], 60.6%-91.8%) and for HPV31/33/45 was 48.7% (95% CI, 20.8%-66.8%). Prevalence of HPV16/18 was compared to findings in 2007-2008 (prevaccination) and to predictions from Public Health England's mathematical model.

Discussion: Eight years after the introduction of a national HPV vaccination program, substantial declines have occurred in HPV16/18 and HPV31/33/45. The prevalence of other high-risk HPV types has not changed.
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http://dx.doi.org/10.1093/infdis/jiy249DOI Listing
August 2018

Effectiveness of herpes zoster vaccination in an older United Kingdom population.

Vaccine 2018 04 17;36(17):2371-2377. Epub 2018 Mar 17.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London, UK.

Background: Vaccination against herpes zoster was introduced in the United Kingdom in 2013 for individuals aged 70 years, with a phased catch-up campaign for 71-79 year olds. Vaccine introduction has resulted in a marked fall in incident herpes zoster and in post-herpetic neuralgia (PHN), but formal evaluation of vaccine effectiveness is needed.

Methods: In a population-based cohort study of older individuals born between 1933 and 1946, we used linked UK anonymised primary care health records for the first three years of the vaccination programme (01/09/2013-31/08/2016) and multivariable Poisson regression to obtain incidence rates and vaccine effectiveness (VE) against zoster and PHN.

Results: Among 516,547 individuals, 21% were vaccinated. Incidence of zoster was 3.15/1000 person-years in vaccinees and 8.80/1000 person-years in unvaccinated individuals. After adjustment, VE was 64% (95%CI = 60-68%) against incident zoster and 81% (95%CI = 61-91%) against PHN, with very similar VE estimates in the routine and catch-up cohorts. VE against zoster was lower in those with a previous history of zoster: 47% (95%CI = 31-58%) versus 64% (95%CI = 60-68%) in those without previous zoster. There was evidence of waning VE over time, from 69% (95%CI = 65-74%) in the first year after vaccination to 45% (95%CI = 29-57%) by the third year.

Conclusion: This first formal assessment of VE in the UK zoster vaccination programme demonstrates good effectiveness of zoster vaccine, and very good protection against PHN. The findings provide evidence that VE is similar across the age groups targeted for vaccination in the UK, and on duration of protection of the vaccine in public health use. The study provides key information for decision-makers about the future direction of UK zoster vaccination programme, indicating that the live zoster vaccine may be more cost-effective than estimated previously. It also supports efforts to communicate the benefits of zoster vaccination to address the declining coverage observed across the UK.
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http://dx.doi.org/10.1016/j.vaccine.2018.02.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5899761PMC
April 2018

Acute kidney injury and infections in patients taking antihypertensive drugs: a self-controlled case series analysis.

Clin Epidemiol 2018 30;10:187-202. Epub 2018 Jan 30.

Department of Non-Communicable Disease Epidemiology.

Background: The relative risk of acute kidney injury (AKI) following different infections, and whether angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) modify the risk, is unclear. We aimed to determine the risks of hospital admission with AKI following infections (urinary tract infection [UTI], lower respiratory tract infection [LRTI], and gastroenteritis) among users of antihypertensive drugs.

Methods: We used UK electronic health records from practices contributing to the Clinical Practice Research Datalink linked to the Hospital Episode Statistics database. We identified adults initiating ACEIs/ARBs or alternative antihypertensive therapy (β-blockers, calcium channel blockers, or thiazide diuretics) between April 1997 and March 2014 with at least 1 year of primary care registration prior to first prescription, who had a hospital admission for AKI, and who had a primary care record for incident UTI, LRTI, or gastroenteritis. We used a self-controlled case series design to calculate age-adjusted incidence rate ratios (IRRs) for AKI during risk periods following acute infection relative to noninfected periods (baseline).

Results: We identified 10,219 eligible new users of ACEIs/ARBs or other antihypertensives with an AKI record. Among these, 2,012 had at least one record for a UTI during follow-up, 2,831 had a record for LRTI, and 651 had a record for gastroenteritis. AKI risk was higher following infection than in baseline noninfectious periods. The rate ratio was highest following gastroenteritis: for the period 1-7 days postinfection, the IRR for AKI following gastroenteritis was 43.4 (95% CI=34.0-55.5), compared with 6.0 following LRTI (95% CI=5.0-7.3), and 9.3 following UTI (95% CI=7.8-11.2). Increased risks were similar for different antihypertensives.

Conclusion: Acute infections are associated with substantially increased transient AKI risk among antihypertensive users, with the highest risk after gastroenteritis. The increase in relative risk is not greater among users of ACEIs/ARBs compared with users of other antihypertensives.
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http://dx.doi.org/10.2147/CLEP.S146757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5796801PMC
January 2018

Do delays in data availability limit the implementation of near real-time vaccine safety surveillance using the Clinical Practice Research Datalink?

Pharmacoepidemiol Drug Saf 2018 01 28;27(1):25-29. Epub 2017 Nov 28.

Statistics, Modelling and Economics Department, Public Health England, London, UK.

Purpose: Near real-time vaccine safety surveillance (NRTVSS) using electronic health records has been used to detect timely vaccine safety signals. Trial implementation of NRTVSS using the Clinical Practice Research Datalink (CPRD) has shown that there is limited power to detect safety signals for rare events. Delays in recording outcomes and receiving data influence the power and timeliness to identify a signal. Our work aimed to compare how different sources of delays influence power and expected time to signal to implement NRTVSS using CPRD.

Methods: We studied seasonal influenza vaccine/Guillain-Barré syndrome and performed power and expected time to signal calculations for the 2013-2014/2014-2015 seasons. We used the Poisson-based maximised sequential probability ratio test, which compares observed-to-expected events. For each study season, we obtained an average Guillain-Barré syndrome/seizures age-sex-adjusted rate from the 5 previous seasons and then used this rate to calculate the expected number of events, assuming a 42-day risk-window. Calculations were performed for detecting rate ratios of 1.5 to 10. We compared power and timeliness considering combinations of the presence/absence of delays in recording outcomes and in receiving data. The R-package Sequential was used.

Results: In general, there was ≥80% power to detect increases in risk of ≥4 at the end of the season. Assuming absence of delays slightly improved power (a maximum increase of 4%) but did not noticeably reduce time to detect a signal.

Conclusion: Removing delays in data availability is insufficient to significantly improve the performance of a NRTVSS system using CPRD. Expansion of CPRD data is required. KEY POINTS The Clinical Practice Research Datalink (CPRD) can be used to implement near real-time vaccine safety surveillance, but there is limited power to detect signals for rare outcomes. Delays in recording outcomes and in receiving data might limit power and timeliness of a system. We assessed the influence of these sources of delays to inform data providers of the steps required to improve a system using CPRD data. Removing delays in recording outcomes and receiving data is unlikely to significantly improve the performance of a system using CPRD data. Expansion of the data available is needed.
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http://dx.doi.org/10.1002/pds.4356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5767762PMC
January 2018

Identifying social factors amongst older individuals in linked electronic health records: An assessment in a population based study.

PLoS One 2017 30;12(11):e0189038. Epub 2017 Nov 30.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.

Identification and quantification of health inequities amongst specific social groups is a pre-requisite for designing targeted healthcare interventions. This study investigated the recording of social factors in linked electronic health records (EHR) of individuals aged ≥65 years, to assess the potential of these data to identify the social determinants of disease burden and uptake of healthcare interventions. Methodology was developed for ascertaining social factors recorded on or before a pre-specified index date (01/01/2013) using primary care data from Clinical Practice Research Datalink (CPRD) linked to hospitalisation and deprivation data in a cross-sectional study. Social factors included: religion, ethnicity, immigration status, small area-level deprivation, place of residence (including communal establishments such as care homes), marital status and living arrangements (e.g. living alone, cohabitation). Each social factor was examined for: completeness of recording including improvements in completeness by using other linked EHR, timeliness of recording for factors that might change over time and their representativeness (compared with English 2011 Census data when available). Data for 591,037 individuals from 389 practices from England were analysed. The completeness of recording varied from 1.6% for immigration status to ~80% for ethnicity. Linkages provided the deprivation data (available for 82% individuals) and improved completeness of ethnicity recording from 55% to 79% (when hospitalisation data were added). Data for ethnicity, deprivation, living arrangements and care home residence were comparable to the Census data. For time-varying variables such as residence and living alone, ~60% and ~35% respectively of those with available data, had this information recorded within the last 5 years of the index date. This work provides methods to identify social factors in EHR relevant to older individuals and shows that factors such as ethnicity, deprivation, not living alone, cohabitation and care home residence can be ascertained using these data. Applying these methodologies to routinely collected data could improve surveillance programmes and allow assessment of health equity in specific healthcare studies.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0189038PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5708811PMC
January 2018

Implementing near real-time vaccine safety surveillance using the Clinical Practice Research Datalink (CPRD).

Vaccine 2017 12 19;35(49 Pt B):6885-6892. Epub 2017 Oct 19.

Statistics, Modelling and Economics Department, Public Health England, London NW9 5 EQ, United Kingdom.

Introduction: Near real-time vaccine safety surveillance (NRTVSS) using electronic health records is increasingly used to rapidly detect vaccine safety signals. NRTVSS has not been fully implemented in the UK. We assessed the feasibility of implementing this surveillance using the UK Clinical Practice Research Datalink (CPRD).

Methods: We selected seasonal influenza vaccine/Guillain-Barré Syndrome (GBS) as an example of a rare outcome and measles-mumps-rubella (MMR) vaccine/febrile seizures as a positive control. For influenza/GBS we implemented a system for the 2013/2014 and 2014/2015 influenza seasons; for MMR/seizures the surveillance period was July 2014-June 2015. We used the continuous Poisson-based maximized sequential probability ratio test (PMaxSPRT), comparing observed-to-expected events, for both pairs. We calculated an age-sex-adjusted rate using 5years of historic data and used this rate to calculate the expected number of events in pre-specified post-vaccination risk-window (GBS: 0-42days, seizures: 6-21days). For MMR/seizures we also implemented the system using the Binominal-based maximized sequential probability ratio test (BMaxSPRT). For this, we compared seizures in the risk-window (6-21days) to a control window (0-5 and 22-32days). Delays in recording outcomes influence the data available, so we adjusted the expected number of events using a historical distribution of delays in recording GBS/febrile seizures. Analyses were run using data up to each CPRD monthly release. We also performed power calculations for detecting increases in relative risk (RR) from 1.5 to 10.

Results: For influenza/GBS we implemented a system in both seasons with no signal. Power to detect a signal was >80% for RR≥4. For MMR/seizures we were able to identify a signal with PMaxSPRT but not with BMaxSPRT. Power≥80% for RR≥2.5 for both tests.

Conclusion: CPRD is a potential data source to implement NRTVSS to exclude large increases in the risk of rare outcomes after seasonal influenza and lower increases in risk for more frequent outcomes.
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http://dx.doi.org/10.1016/j.vaccine.2017.09.022DOI Listing
December 2017

Mood Disorders and Risk of Herpes Zoster in 2 Population-Based Case-Control Studies in Denmark and the United Kingdom.

Am J Epidemiol 2018 05;187(5):1019-1028

Research Unit for General Practice, Department of Public Health, Aarhus University, Aarhus, Denmark.

We examined the association between mood disorders and risk of herpes zoster in two case-control studies using data from nationwide Danish registries and practices in the UK Clinical Practice Research Datalink. We included incident zoster cases diagnosed in general practice (using systemic antivirals as a proxy in Denmark) or hospital during 1997-2013 in Denmark (n = 190,671) and during 2000-2013 in the United Kingdom (n = 177,361). We risk-set sampled 4 matched population controls per case. Conditional logistic regression analyses adjusting for zoster risk factors showed that the odds ratios for previous mood disorder among cases versus controls were 1.15 (99% confidence interval (CI): 1.12, 1.19; prevalence 7.1% vs. 6.0%) in Denmark and 1.12 (99% CI: 1.11, 1.14; prevalence 31.6% vs. 29.2%) in the United Kingdom. In Denmark, odds ratios were higher for anxiety (1.23; 99% CI: 1.17, 1.30) and severe stress and adjustment disorder (1.24; 99% CI: 1.18, 1.30) than for depression (1.11; 99% CI: 1.07, 1.14). In the United Kingdom, odds ratios for these conditions were similar: 1.12 (99% CI: 1.10, 1.13), 1.12 (99% CI: 1.10, 1.14), and 1.14 (99% CI: 1.10, 1.19) for depression, anxiety, and severe stress and adjustment disorder, respectively. In conclusion, mood disorders were associated with an increased risk of zoster.
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http://dx.doi.org/10.1093/aje/kwx338DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968637PMC
May 2018

A cohort study of low birth weight and health outcomes in the first year of life, Ghana.

Bull World Health Organ 2017 Aug 26;95(8):574-583. Epub 2017 May 26.

Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, England.

Objective: To investigate the effect of birth weight on infant mortality, illness and care seeking in rural Ghana.

Methods: Using randomized controlled trial data, we compared infants weighing 2.00-2.49, 1.50-1.99 and < 1.50 kg with non-low-birth-weight infants. We generated adjusted mortality hazard ratios (aHR), adjusted illness rate ratios (aRR) and adjusted odds ratios (aOR) for health-facility admissions and absence of care seeking for four time periods: infancy, the neonatal period, early infancy and late infancy - represented by ages of 0-364, 0-27, 28-182 and 183-364 days, respectively.

Findings: Among 22 906 infants, compared with non-low-birth-weight infants: (i) infants weighing 2.00-2.49, 1.50-1.99 and < 1.50 kg were about two (aHR: 2.13; 95% confidence interval, CI: 1.76-2.59), eight (aHR: 8.21; 95% CI: 6.26-10.76) and 25 (aHR: 25.38; 95% CI: 18.36-35.10) times more likely to die in infancy, respectively; (ii) those born weighing < 1.50 kg were about 48 (aHR: 48.45; 95% CI: 32.81-71.55) and eight (aHR: 8.42; 95% CI: 3.09-22.92) times more likely to die in the neonatal period and late infancy, respectively; (iii) those born weighing 1.50-1.99 kg (aRR: 1.57; 95% CI: 1.27-1.95) or < 1.50 kg (aRR: 1.58; 95% CI: 1.13-2.21) had higher neonatal illness rates; and (iv) for those born weighing 1.50-1.99 kg, care was less likely to be sought in the neonatal period (aOR: 3.30; 95% CI: 1.98-5.48) and early infancy (aOR : 1.74; 95% CI: 1.26-2.39).

Conclusion: For low-birth-weight infants in Ghana, strategies to minimize mortality and improve care seeking are needed.
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http://dx.doi.org/10.2471/BLT.16.180273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5537746PMC
August 2017

Association between human herpesvirus infections and dementia or mild cognitive impairment: a systematic review protocol.

BMJ Open 2017 06 23;7(6):e016522. Epub 2017 Jun 23.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Introduction: Persisting neurotropic viruses are proposed to increase the risk of dementia, but evidence of association from robust, adequately powered population studies is lacking. This is essential to inform clinical trials of targeted preventive interventions.

Methods And Analysis: We will carry out a comprehensive systematic review of published and grey literature of the association between infection with, reactivation of, vaccination against or treatment of any of the eight human herpesviruses and dementia or mild cognitive impairment. We will search the Cochrane Library, Embase, Global Health, Medline, PsycINFO, Scopus, Web of Science, clinical trials registers, the New York Academy of Medicine Grey Literature Report, Electronic Theses Online Service through the British Library and the ISI Conference Proceedings Citation Index for randomised controlled trials, cohort, caseâ€"control, case crossover or self-controlled case series studies reported in any language up to January 2017. Titles, abstracts and full-text screening will be conducted by two researchers independently. Data will be extracted systematically from eligible studies using a piloted template. We will assess risk of bias of individual studies in line with the Cochrane Collaboration tool. We will conduct a narrative synthesis, grouping studies by exposure and outcome definitions, and will describe any differences by population subgroups and dementia subtypes. We will consider performing meta-analyses if there are adequate numbers of sufficiently homogeneous studies. The overall quality of cumulative evidence will be assessed using selected Grading of Recommendations, Assessment, Development and Evaluations criteria.

Ethics And Dissemination: As this is a review of existing studies, no ethical approval is required. Results will be disseminated through a peer-reviewed publication and at national and international conferences. We anticipate the review will clarify the current extent and quality of evidence for a link between herpesviruses and dementia, identify gaps and inform the direction of future research.

Prospero Registration Number: CRD42017054684.
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http://dx.doi.org/10.1136/bmjopen-2017-016522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726086PMC
June 2017

The association between human herpesvirus infections and stroke: a systematic review protocol.

BMJ Open 2017 05 29;7(5):e016427. Epub 2017 May 29.

Faculty of Epidemiology & Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Introduction: After primary infection, human herpesviruses establish latency and persist lifelong. Periodic virus reactivation can lead to serious inflammatory complications. Recent research suggests that herpesvirus reactivation may also be linked to acute stroke. An improved understanding of this relationship is vital to inform public health prevention strategies. We will review the evidence regarding the role of human herpesviruses in triggering stroke.

Methods And Analysis: A systematic literature review of published and grey literature studies with a human herpesvirus (infection or reactivation) as an exposure and stroke as an outcome will be carried out. Randomised controlled trials, cohort, case-control, case crossover and self-controlled case series designs will be eligible; no restrictions will be placed on publication status, language and geographical or healthcare setting. The Cochrane Central Register of Controlled Trials, Embase, Global Health, Medline, Scopus and Web of Science will be searched from dates of inception to January 2017. A prespecified search strategy of medical subject headings and free text terms (in the title and abstract) for human herpesviruses AND stroke will be used. Two reviewers will independently screen titles and abstracts for eligible studies, followed by full-text screening. The reviewers will then extract data from the eligible studies using standardised, pilot-tested tables and assess risk of bias in individual studies, in line with the Cochrane Collaboration approach. The data will be synthesised in a narrative format, and meta-analyses considered where there are sufficient data. Quality of evidence will be assessed in line with theGrading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

Ethics And Dissemination: As this is a systematic review, ethical approval is not required. The results will be submitted for peer-review publication and presented at national conferences. A lay and short summary will be disseminated on appropriate webpages.

Prospero Registration Number: CRD42017054502.
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http://dx.doi.org/10.1136/bmjopen-2017-016427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726106PMC
May 2017

Do influenza and pneumococcal vaccines prevent community-acquired respiratory infections among older people with diabetes and does this vary by chronic kidney disease? A cohort study using electronic health records.

BMJ Open Diabetes Res Care 2017 3;5(1):e000332. Epub 2017 Apr 3.

Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.

Objective: We aimed to estimate the effectiveness of influenza and 23-valent pneumococcal polysaccharide vaccination on reducing the burden of community-acquired lower respiratory tract infection (LRTI) among older people with diabetes, and whether this varied by chronic kidney disease (CKD) status.

Research Design And Methods: We used linked UK electronic health records for a retrospective cohort study of 190 492 patients ≥65 years with diabetes mellitus and no history of renal replacement therapy, 1997-2011. We included community-acquired LRTIs managed in primary or secondary care. Infection incidence rate ratios were estimated using the Poisson regression. Pneumococcal vaccine effectiveness (VE) was calculated as (1-effect measure). To estimate influenza VE, a ratio-of-ratios analysis (winter effectiveness/summer effectiveness) was used to address confounding by indication. Final VE estimates were stratified according to estimated glomerular filtration rate and proteinuria status.

Results: Neither influenza nor pneumococcal vaccine uptake varied according to CKD status. Pneumococcal VE was 22% (95% CI 11% to 31%) against community-acquired pneumonia for the first year after vaccination, but was negligible after 5 years. In the ratio-of-ratios analysis, current influenza vaccination had 7% effectiveness for preventing community-acquired LRTI (95% CI 3 to 12). Pneumococcal VE was lower among patients with a history of proteinuria than among patients without proteinuria (p=0.04), but otherwise this study did not identify variation in pneumococcal or influenza VE by markers of CKD.

Conclusions: The public health benefits of influenza vaccine may be modest among older people with diabetes. Pneumococcal vaccination protection against community-acquired pneumonia declines swiftly: alternative vaccination schedules should be investigated.
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http://dx.doi.org/10.1136/bmjdrc-2016-000332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5387965PMC
April 2017

Risk factors for developing acute kidney injury in older people with diabetes and community-acquired pneumonia: a population-based UK cohort study.

BMC Nephrol 2017 May 1;18(1):142. Epub 2017 May 1.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, WC1E7HT, UK.

Background: Acute kidney injury (AKI) is being increasingly recognised in ageing populations. There are a paucity of data about AKI risk factors among older individuals with diabetes and infections, who are at particularly high risk of AKI. The objective of this study was to evaluate the risk factors for developing acute kidney injury (AKI) amongst older patients with diabetes and community-acquired pneumonia (CAP) in England, and whether the impact of underlying kidney function varied with age.

Methods: This was a population-based retrospective cohort study over 7 years (01/04/2004-31/3/2011) using electronic health records from the Clinical Practice Research Datalink linked to Hospital Episode Statistics. The study population comprised individuals with diabetes aged ≥65 years with CAP. Associations between demographic, lifestyle factors, co-morbidities and medications and development of AKI within 28 days of CAP were explored in a logistic regression model.

Results: Among 3471 patients with CAP and complete covariate data, 298 patients developed subsequent AKI. In multivariable analyses, factors found to be independently associated with AKI included: male sex (adjusted odds ratio, aOR: 1.56 95% confidence interval (CI): 1.20-2.04), hypertension (aOR1.36 95% CI 1.01-1.85), being prescribed either angiotensin-converting-enzyme inhibitors or angiotensin-II-receptor-blockers (aOR: 1.59 95% CI: 1.19-2.13), or insulin (aOR: 2.27 95% CI: 1.27-4.05), presence of proteinuria (aOR 1.27 95% CI 0.98-1.63), and low estimated glomerular filtration rate (eGFR). The odds of AKI were more graded amongst older participants aged ≥80 years compared to those of younger age: for eGFR of ≤29 mL/min/1.73m (vs 60 ml/min/1.73m) aOR: 5.51 95% CI 3.28-9.27 and for eGFR 30-59 mL/min/1.73m 1.96 95% CI 1.30-2.96, whilst any eGFR < 60 ml/min/1.73m was associated with approximately 3-fold increase in the odds of AKI amongst younger individuals (p-value for interaction = 0.007).

Conclusions: The identified risk factors should help primary care and hospital providers identify high risk patients in need of urgent management including more intensive monitoring, and prevention of AKI following pneumonia.
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http://dx.doi.org/10.1186/s12882-017-0566-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5412062PMC
May 2017

Lower vaccine uptake amongst older individuals living alone: A systematic review and meta-analysis of social determinants of vaccine uptake.

Vaccine 2017 04 27;35(18):2315-2328. Epub 2017 Mar 27.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. Electronic address:

Introduction: Vaccination is a key intervention to reduce infectious disease mortality and morbidity amongst older individuals. Identifying social factors for vaccine uptake enables targeted interventions to reduce health inequalities.

Objective: To systematically appraise and quantify social factors associated with vaccine uptake amongst individuals aged ≥60years from Europe.

Methods: We searched Medline and Embase from inception to 24/02/2016. The association of vaccine uptake was examined for social factors relevant at an individual level, to provide insight into individuals' environment and enable development of targeted interventions by healthcare providers to deliver equitable healthcare. Factors included: living alone, marital status, education, income, vaccination costs, area-level deprivation, social class, urban versus rural residence, immigration status and religion. Between-study heterogeneity for each factor was identified using I-statistics and Q-statistics, and investigated by stratification and meta-regression analysis. Meta-analysis was conducted, when appropriate, using fixed- or random-effects models.

Results: From 11,754 titles, 35 eligible studies were identified (uptake of: seasonal influenza vaccine (SIV) only (n=27) or including pneumococcal vaccine (PV) (n=5); herpes zoster vaccine (n=1); pandemic influenza vaccine (n=1); PV only (n=1)). Higher SIV uptake was reported for individuals not living alone (summary odds ratios (OR)=1.39 (95% confidence interval (CI): 1.16-1.68). Lower SIV uptake was observed in immigrants and in more deprived areas: summary OR=0.57 (95%CI: 0.47-0.68) and risk ratio=0.93 (95%CI: 0.92-0.94) respectively. Higher SIV uptake was associated with higher income (OR=1.26 (95%CI: 1.08-1.47)) and higher education (OR=1.05 (95%CI: 1-1.11)) in adequately adjusted studies. Between-study heterogeneity did not appear to result from variation in categorisation of social factors, but for education was partly explained by varying vaccination costs (meta-regression analysis p=<0.0001); individuals with higher education had higher vaccine uptake in countries without free vaccination.

Conclusions: Quantification of associations between social factors and lower vaccine uptake, and notably living alone (an overlooked factor in vaccination programmes), should enable health professionals target specific social groups to tackle vaccine-related inequalities.
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http://dx.doi.org/10.1016/j.vaccine.2017.03.013DOI Listing
April 2017

Assessing recording delays in general practice records to inform near real-time vaccine safety surveillance using the Clinical Practice Research Datalink (CPRD).

Pharmacoepidemiol Drug Saf 2017 Apr 3;26(4):437-445. Epub 2017 Feb 3.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Purpose: Near real-time vaccine safety surveillance (NRTVSS) is an option for post-licensure vaccine safety assessment. NRTVSS requires timely recording of outcomes in the database used. Our main objective was to examine recording delays in the Clinical Practice Research Datalink (CPRD) for outcomes of interest for vaccine safety to inform the feasibility of NRTVSS using these data. We also evaluated completeness of recording and further assessed reporting delays for hospitalized events in CPRD.

Methods: We selected Guillain-Barré syndrome (GBS), Bell's palsy (BP), optic neuritis (ON) and febrile seizures (FS), from January 2005 to June 2014. We assessed recording delays (e.g. due to feedback from specialist referral) in stand-alone CPRD by comparing the event and system dates and excluding delays >1 year. We used linked CPRD-hospitalization data to further evaluate delays and completeness of recording in CPRD.

Results: Among 51 220 patients for the stand-alone CPRD analysis (GBS: n = 830; BP: n = 12 602; ON: n = 1720; and FS: n = 36 236), most had a record entered within 1 month of the event date (GBS: 73.6%; BP: 93.4%; ON: 76.2%; and FS: 85.6%). A total of 13 482 patients, with a first record in hospital, were included for the analysis of linked data (GBS: n = 678; BP: n = 4060; ON: n = 485; and FS: n = 8321). Of these, <50% had a record in CPRD after 1 year (GBS: 41.3%; BP: 22.1%; ON: 22.4%; and FS: 41.8%).

Conclusion: This work shows that most diagnoses in CPRD for the conditions examined were recorded with delays of ≤30 days, making NRTVSS possible. The pattern of delays was condition-specific and could be used to adjust for delays in the NRTVSS analysis. Despite low sensitivity of recording, implementing NRTVSS in CPRD is worthwhile and could be carried out, at least on a trial basis, for events of interest. © 2017 The Authors. Pharmacoepidemiology & Drug Safety Published by John Wiley & Sons Ltd.
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http://dx.doi.org/10.1002/pds.4173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5396331PMC
April 2017

Impact of the national rotavirus vaccination programme on acute gastroenteritis in England and associated costs averted.

Vaccine 2017 01 20;35(4):680-686. Epub 2016 Dec 20.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; Immunisation, Hepatitis and Blood Safety Department, Centre for Infectious Disease Surveillance and Control (CIDSC), Public Health England, 61 Colindale Avenue, London NW9 5EQ, UK.

Background: Introduction of infant oral rotavirus vaccination in the UK in July 2013 has resulted in decreased hospitalisations and Emergency Department (ED) visits for acute gastroenteritis (AGE), for both adults and children. We investigated reductions in AGE incidence seen in primary care in the two years after vaccine introduction, and estimated the healthcare costs averted across healthcare settings in the first year of the vaccination programme.

Methods: We used primary care data from the Clinical Practice Research Datalink and age-stratified time-series analyses to derive adjusted incidence rate ratios (IRR) for AGE in the first two years of the post-vaccination era (July 2013-April 2015) compared to the pre-vaccination era (July 2008-June 2013). We estimated cases averted among children aged <5years in the first year of the vaccination programme by comparing observed numbers of AGE cases in 2013-2014 to numbers predicted from the time-series models. We then estimated the healthcare costs averted for general practice consultations, ED visits and hospitalisations.

Results: In general practice, AGE rates in infants (the target group for vaccination) decreased by 15% overall after vaccine introduction (IRR=0.85; 95%CI=0.76-0.95), and by 41% in the months of historically high rotavirus circulation (IRR=0.59; 95%CI=0.53-0.66). Rates also decreased in other young children and to a lesser degree in older individuals, indicating herd immunity. Across all three settings (general practice, EDs, and hospitalisations) an estimated 87,376 (95% prediction interval: 62,588-113,561) AGE visits by children aged <5years were averted in 2013-14, associated with an estimated £12.5million (9,209-16,198) reduction in healthcare costs.

Conclusions: The marked decreases in the general practice AGE burden after rotavirus vaccine introduction mirror decreases seen in other UK healthcare settings. Overall, these decreases are associated with substantial averted healthcare costs.
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http://dx.doi.org/10.1016/j.vaccine.2016.11.057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5267482PMC
January 2017

Partner Bereavement and Risk of Herpes Zoster: Results from Two Population-Based Case-Control Studies in Denmark and the United Kingdom.

Clin Infect Dis 2017 03;64(5):572-579

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, United Kingdom.

Background: Psychological stress is commonly thought to increase the risk of herpes zoster by causing immunosuppression. However, epidemiological studies on the topic are sparse and inconsistent. We conducted 2 parallel case-control studies of the association between partner bereavement and risk of zoster using electronic healthcare data covering the entire Danish population and general practices in the UK Clinical Practice Research Datalink.

Methods: We included patients with a zoster diagnosis from the primary care or hospital-based setting in 1997-2013 in Denmark (n = 190671) and 2000-2013 in the United Kingdom (n = 150207). We matched up to 4 controls to each case patient by age, sex, and general practice (United Kingdom only) using risk-set sampling. The date of diagnosis was the index date for case patients and their controls. We computed adjusted odds ratios with 99% confidence intervals for previous bereavement among case patients versus controls using conditional logistic regression with results from the 2 settings pooled using random-effects meta-analysis.

Results: Overall, the adjusted odds ratios for the association between partner bereavement and zoster were 1.05 (99% confidence interval, 1.03-1.07) in Denmark and 1.01 (.98-1.05) in the United Kingdom. The pooled estimates were 0.72, 0.90, 1.10, 1.08, 1.02, 1.04, and 1.03 for bereavement within 0-7, 8-14, 15-30, 31-90, 91-365, 366-1095, and >1095 days before the index date, respectively.

Conclusions: We found no consistent evidence of an increased risk of zoster after partner death. Initial fluctuations in estimates may be explained by delayed healthcare contact due to the loss.
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http://dx.doi.org/10.1093/cid/ciw840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5850543PMC
March 2017

Recording of hospitalizations for acute exacerbations of COPD in UK electronic health care records.

Clin Epidemiol 2016 21;8:771-782. Epub 2016 Nov 21.

Respiratory Epidemiology, Occupational Medicine and Public Health, National Heart and Lung Institute, Imperial College London, London, UK; Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Background: Accurate identification of hospitalizations for acute exacerbations of chronic obstructive pulmonary disease (AECOPD) within electronic health care records is important for research, public health, and to inform health care utilization and service provision. We aimed to develop a strategy to identify hospitalizations for AECOPD in secondary care data and to investigate the validity of strategies to identify hospitalizations for AECOPD in primary care data.

Methods: We identified patients with chronic obstructive pulmonary disease (COPD) in the Clinical Practice Research Datalink (CPRD) with linked Hospital Episodes Statistics (HES) data. We used discharge summaries for recent hospitalizations for AECOPD to develop a strategy to identify the recording of hospitalizations for AECOPD in HES. We then used the HES strategy as a reference standard to investigate the positive predictive value (PPV) and sensitivity of strategies for identifying AECOPD using general practice CPRD data. We tested two strategies: 1) codes for hospitalization for AECOPD and 2) a code for AECOPD other than hospitalization on the same day as a code for hospitalization due to unspecified reason.

Results: In total, 27,182 patients with COPD were included. Our strategy to identify hospitalizations for AECOPD in HES had a sensitivity of 87.5%. When compared with HES, using a code suggesting hospitalization for AECOPD in CPRD resulted in a PPV of 50.2% (95% confidence interval [CI] 48.5%-51.8%) and a sensitivity of 4.1% (95% CI 3.9%-4.3%). Using a code for AECOPD and a code for hospitalization due to unspecified reason resulted in a PPV of 43.3% (95% CI 42.3%-44.2%) and a sensitivity of 5.4% (95% CI 5.1%-5.7%).

Conclusion: Hospitalization for AECOPD can be identified with high sensitivity in the HES database. The PPV and sensitivity of strategies to identify hospitalizations for AECOPD in primary care data alone are very poor. Primary care data alone should not be used to identify hospitalizations for AECOPD. Instead, researchers should use data that are linked to data from secondary care.
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http://dx.doi.org/10.2147/CLEP.S117867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123723PMC
November 2016

Increased rates of sequelae post-encephalitis in individuals attending primary care practices in the United Kingdom: a population-based retrospective cohort study.

J Neurol 2017 Feb 20;264(2):407-415. Epub 2016 Oct 20.

London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK.

The true extent of sequelae in encephalitis survivors relative to rates within the general population is not known. This study aimed to quantify increased risks of epilepsy, depressive disorders, anxiety disorders, psychotic disorders, bipolar disorder, cognitive problems, dementia, headache, and alcohol abuse among encephalitis cases. 2460 exposed individuals diagnosed with incident encephalitis in the Clinical Practice Research Datalink and 47,914 unexposed individuals without a history of encephalitis were included. Multivariable Poisson regression was used to estimate adjusted rate ratios in individuals with encephalitis compared to the general population and to estimate whether the effect of these outcomes varied over time. Individuals with encephalitis had an increased risk of all investigated outcomes. The highest RR was seen for epilepsy (adjusted RR 31.9; 95 % confidence interval 25.38-40.08), whereas the lowest was seen for anxiety disorders (1.46, 1.27-1.68). The second highest RRs were for particular psychiatric illnesses, including bipolar disorder (6.34, 3.34-12.04) and psychotic disorders (3.48, 2.18-5.57). The RR was highest in the first year of follow-up for all outcomes except headache; this was particularly true for epilepsy (adjusted RR in first year of follow-up 139.6, 90.62-215.03). This study shows that sequelae are common in survivors of encephalitis. We confirm the presence of outcomes more commonly linked to encephalitis and describe those less commonly identified as being associated with encephalitis. The results of this study have important implications for the management of encephalitis patients and for the design of tertiary prevention strategies, as many of these sequelae are treatable.
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http://dx.doi.org/10.1007/s00415-016-8316-8DOI Listing
February 2017

Population-Level Effects of Human Papillomavirus Vaccination Programs on Infections with Nonvaccine Genotypes.

Emerg Infect Dis 2016 10;22(10):1732-40

We analyzed human papillomavirus (HPV) prevalences during prevaccination and postvaccination periods to consider possible changes in nonvaccine HPV genotypes after introduction of vaccines that confer protection against 2 high-risk types, HPV16 and HPV18. Our meta-analysis included 9 studies with data for 13,886 girls and women ≤19 years of age and 23,340 women 20-24 years of age. We found evidence of cross-protection for HPV31 among the younger age group after vaccine introduction but little evidence for reductions of HPV33 and HPV45. For the group this same age group, we also found slight increases in 2 nonvaccine high-risk HPV types (HPV39 and HPV52) and in 2 possible high-risk types (HPV53 and HPV73). However, results between age groups and vaccines used were inconsistent, and the increases had possible alternative explanations; consequently, these data provided no clear evidence for type replacement. Continued monitoring of these HPV genotypes is important.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5038419PMC
http://dx.doi.org/10.3201/eid2210.160675DOI Listing
October 2016

Bronchiectasis and the risk of cardiovascular disease: a population-based study.

Thorax 2017 02 29;72(2):161-166. Epub 2016 Aug 29.

Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.

Background: There are limited data on the burden of cardiovascular comorbidities in people with bronchiectasis. Our cross-sectional study estimates the burden of pre-existing diagnoses of coronary heart disease (CHD) and stroke in people with bronchiectasis compared with the general population. The historical cohort study investigates if individuals with bronchiectasis are at increased risk of incident CHD and stroke events.

Methods: We used primary care electronic records from the Clinical Practice Research Datalink. The cross-sectional study used logistic regression to quantify the association between bronchiectasis and recorded diagnoses of CHD or stroke. Cox regression was used to investigate if people with bronchiectasis experienced increased incident CHD and strokes compared with the general population, adjusting for age, sex, smoking habit and other risk factors for cardiovascular disease.

Results: Pre-existing diagnoses of CHD (OR 1.33, 95% CI 1.25 to 1.41) and stroke (OR 1.92, 95% CI 1.85 to 2.01) were higher in people with bronchiectasis compared with those without bronchiectasis, after adjusting for age, sex, smoking and risk factors for cardiovascular disease. The rate of first CHD and stroke were also higher in people with bronchiectasis (HR for CHD 1.44 (95% CI 1.27 to 1.63) and HR for stroke 1.71 (95% CI 1.54 to 1.90)).

Conclusion: The risk of CHD and stroke are higher among people with bronchiectasis compared with the general population. An increased awareness of these cardiovascular comorbidities in this population is needed to provide a more integrated approach to the care of these patients.
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http://dx.doi.org/10.1136/thoraxjnl-2015-208188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5284336PMC
February 2017
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