Publications by authors named "Vu Dinh Thiem"

62 Publications

Immunogenicity and safety of a nine-valent human papillomavirus vaccine in Vietnamese males and females (9 to 26 years of age): an open-label, phase 3 trial.

Hum Vaccin Immunother 2021 Apr 12:1-6. Epub 2021 Apr 12.

Merck & Co., Inc., Kenilworth, NJ, USA.

This open-label, single-center, Phase 3 study (NCT03546842) assessed the immunogenicity and safety of the nine-valent human papillomavirus (9vHPV; HPV6/11/16/18/31/33/45/52/58) vaccine in Vietnamese males and females, with the aim to support 9vHPV vaccine licensure in Vietnam. Participants aged 9-26 years received three 9vHPV vaccine doses (Day 1, Month 2, Month 6). Serum samples were obtained on Day 1 (pre-vaccination) and at Month 7 (one month post-Dose 3) for the measurement of anti-HPV antibodies. Geometric mean titers (GMTs) and seroconversion percentages were obtained using the HPV-9 competitive Luminex immunoassay. Injection-site adverse events (AEs), systemic AEs, serious AEs (SAEs), and study discontinuations due to AEs were recorded. Of 201 participants enrolled, 200 (99.5%) received ≥1 vaccine dose. All participants who received the three-dose regimen (198/200, 98.5%) seroconverted for all 9vHPV vaccine types by Month 7. Robust anti-HPV GMT responses were also observed. Half of participants (50.5%) reported ≥1 AE; the majority were injection-site-related (45.0%) and mild (43.0%). There were no deaths, vaccine-related SAEs, or discontinuations due to AEs. Administration of three 9vHPV vaccine doses was highly immunogenic and resulted in acceptable seropositivity percentages for all vaccine HPV types. The 9vHPV vaccine was generally well tolerated among this study population.: Vietnam: clinicaltrials.gov Identifier NCT03546842.
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http://dx.doi.org/10.1080/21645515.2020.1865739DOI Listing
April 2021

Molecular epidemiology of Cryptosporidium spp. in an agricultural area of northern Vietnam: A community survey.

Parasitol Int 2021 Apr 2;83:102341. Epub 2021 Apr 2.

Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, 207 Uehara, Nishiharacho, Okinawa 903-0215, Japan.

The purpose of this study was to investigate the occurrence of Cryptosporidium infection and the potential for transmission of Cryptosporidium spp. between animals and humans in northern Vietnam. A total of 2715 samples (2120 human diarrheal samples, 471 human non-diarrheal samples, and 124 animal stool samples) were collected through our community survey in an agricultural area. All samples were tested for Cryptosporidium spp. by direct immunofluorescence assay (DFA) using a fluorescent microscope. DNA extraction, PCR amplification of three genes (COWP, SSU-rRNA, and GP60), and sequencing analysis were performed to identify Cryptosporidium spp. Of 2715 samples, 15 samples (10 diarrheal samples, 2 non-diarrheal samples, and 3 animal stool samples) tested positive by PCR for the COWP gene. Three species of Cryptosporidium spp. were identified as C. canis (from six human diarrheal samples, two human non-diarrheal samples, and one dog sample), C. hominis (from four human diarrheal samples), and C. suis (from two pig samples) by sequencing the amplified COWP and/or SSU-rRNA genes. In terms of C. hominis, the GP60 subtype IeA12G3T3 was detected in all four human diarrheal samples. Although the number of positive samples was very small, our epidemiological data showed that the emerging pattern of each of the three species (C. canis, C. hominis, and C. suis) was different at this study site. While C. hominis and C. suis were only detected in human and pig samples, respectively, C. canis was detected in samples from both dogs and humans. We suspect that C. canis infections in humans at this study site may be due to environmental contamination with animal and human feces.
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http://dx.doi.org/10.1016/j.parint.2021.102341DOI Listing
April 2021

Safety of a quadrivalent influenza vaccine in Vietnamese healthy subjects aged 6 months and older.

Hum Vaccin Immunother 2021 Mar 12;17(3):690-693. Epub 2020 Aug 12.

Sanofi Pasteur Medical Asia and JPAC, Sanofi-Aventis (Singapore) Pte. Ltd, Singapore, Singapore.

Quadrivalent influenza vaccines (QIVs) provide protection against the two influenza A viruses (H1N1 and H3N2) and both co-circulating influenza B lineages. QIVs have been found safe, immunogenic, and efficacious in several phase III clinical trials. Here we assess the safety of QIV after vaccination in Vietnamese infants, children, and adults. Participants (n = 228) were asked to report any solicited adverse events (AEs) occurring within 7 days, unsolicited non-serious AEs occurring within 28 days post-vaccination, and serious adverse events (SAEs) at any time during the study. The study was completed by 224 participants (97.4%). Thirty-one children (39.7%) aged 6 - 35 months, 32 children (40.0%) aged 3 - 8 years, 2 participants (9.0%) aged 9 - 17 years, 5 participants (17.9%) aged 18 - 60 years, and 3 participants (15.0%) aged ≥60 years reported ≥1 solicited reaction within 7 days following vaccination. The most frequent-solicited AEs were injection-site tenderness or pain, appetite loss, fever, and abnormal crying in 6 - 35 month-olds, and fever, headache, and myalgia in other age groups. No severe-unsolicited AEs or vaccine-related SAEs were reported. These results suggest that QIV is well tolerated across age groups in Vietnam, and can be safely used to protect the Vietnamese population against influenza and its potentially serious complications.
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http://dx.doi.org/10.1080/21645515.2020.1795477DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7993207PMC
March 2021

Author Correction: Exposure to paternal tobacco smoking increased child hospitalization for lower respiratory infections but not for other diseases in Vietnam.

Sci Rep 2020 Apr 6;10(1):6162. Epub 2020 Apr 6.

Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41598-020-62383-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136198PMC
April 2020

A Phase 2/3 double blinded, randomized, placebo-controlled study in healthy adult participants in Vietnam to examine the safety and immunogenicity of an inactivated whole virion, alum adjuvanted, A(H5N1) influenza vaccine (IVACFLU-A/H5N1).

Vaccine 2020 02 4;38(6):1541-1550. Epub 2019 Dec 4.

PATH, Seattle, USA. Electronic address:

Background: A global shortfall of vaccines for avian influenza A(H5N1) would occur, especially in low- and-middle income countries, if a pandemic were to occur. To address this issue, development of a pre-pandemic influenza vaccine was initiated in 2012, leveraging a recently established influenza vaccine manufacturing capacity in Vietnam.

Methods: This was a Phase 2/3, double-blinded, randomized, placebo-controlled study to test the safety and immunogenicity of IVACFLU-A/H5N1 vaccine in healthy adults. Phase 2 was a dose selection study, in which 300 participants were randomized to one of the three groups (15 mcg, 30 mcg, or placebo). Safety and immunogenicity were assessed in all participants. In Phase 3, 630 participants were randomized to receive the IVACFLU-A/H5N1 vaccine dose selected in Phase 2 (15 mcg, n = 525) or placebo (n = 105). Safety was assessed in all Phase 3 participants and immunogenicity was measured in a subset of participants.

Results: The vaccine was well tolerated and most of the adverse events were mild and of short duration. Mild pain at the injection site was the most common adverse event seen in 60 percent of participants in the vaccine group in Phase 3. In Phase 2, both 15 mcg and 30 mcg doses were immunogenic, so the lower dose was selected for further testing in Phase 3. In Phase 3 overall seroconversion rates were 68 percent for hemagglutination inhibition (HI), 51 percent for microneutralization (MN) and 56 percent for single radial hemolysis (SRH). The seroprotection rates were 44 percent for HI, 41 percent for MN and 55 percent for SRH. The GMT ratio was 5.31 and 3.7 for HI and MN respectively; GMA was 4.75 for the SRH.

Conclusion: The IVACFLU A/H5N1 was safe and immunogenic. Development of this pandemic avian influenza vaccine is a welcome addition to the limited global pool of these vaccines. ClinicalTrials.gov register NCT02612909.
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http://dx.doi.org/10.1016/j.vaccine.2019.11.059DOI Listing
February 2020

Effect of Vitamin D supplementation to reduce respiratory infections in children and adolescents in Vietnam: A randomized controlled trial.

Influenza Other Respir Viruses 2019 03 4;13(2):176-183. Epub 2019 Jan 4.

Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.

Background: It is uncertain whether vitamin D can reduce respiratory infection.

Objective: To determine whether vitamin D supplementation reduces influenza and other upper viral respiratory tract infections.

Methods: A total of 1300 healthy children and adolescents between the ages of 3 and 17 years were randomized to vitamin D (14 000 U weekly) or placebo for 8 months in Vietnam. The primary outcome was reverse transcriptase (RT)-PCR-confirmed influenza infection, and the coprimary outcome was multiplex PCR-confirmed non-influenza respiratory viruses. Participants, caregivers, and those assessing outcomes were blinded to group assignment.

Results: A total of 650 children and adolescents were randomly assigned to vitamin D and 650 to placebo. The mean baseline serum 25-hydroxyvitamin D levels were 65.7 nmol/L and 65.2 nmol/L in the intervention and placebo groups, respectively, with an increase to 91.8 nmol/L in the vitamin D group and no increase, 64.5 nmol/L, in the placebo group. All 1300 participants randomized contributed to the analysis. We observed RT-PCR-confirmed influenza A or B occurred in 50 children (7.7%) in the vitamin D group and in 43 (6.6%) in the placebo group (hazard ratio [HR]: 1.18, 95% CI: 0.79-1.78). RT-PCR-confirmed non-influenza respiratory virus infection occurred in 146 (22.5%) in the vitamin D group and in 185 (28.5%) in the placebo group (hazard ratio [HR]: 0.76, 95% CI: 0.61-0.94). When considering all respiratory viruses, including influenza, the effect of vitamin D in reducing infection was significant, HR: 0.81, 95% CI: 0.66-0.99.

Conclusion: Vitamin D supplementation did not reduce the incidence of influenza but moderately reduced non-influenza respiratory viral infection.
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http://dx.doi.org/10.1111/irv.12615DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6379634PMC
March 2019

Seasonality of respiratory viruses causing hospitalizations for acute respiratory infections in children in Nha Trang, Vietnam.

Int J Infect Dis 2018 Oct 14;75:18-25. Epub 2018 Aug 14.

Institute of Tropical Medicine, Nagasaki University, Japan.

Background: Acute respiratory infections (ARIs) are the most common causes of death in children under 5 years of age. While the etiology of most pneumonia and ARI episodes is undiagnosed, a broad range of ARI-causing viruses circulate widely in South East Asia. However, the patterns and drivers of the seasonal transmission dynamics are largely unknown. Here we identify the seasonal patterns of multiple circulating viruses associated with hospitalizations for ARIs in Nha Trang, Vietnam.

Methods: Hospital based enhanced surveillance of childhood ARI is ongoing at Khanh Hoa General Hospital in Nha Trang. RT-PCR was performed to detect 13 respiratory viruses in nasopharyngeal samples from enrolled patients. Seasonal patterns of childhood ARI hospital admissions of various viruses were assessed, as well as their association with rainfall, temperature, and dew point.

Results: Respiratory syncytial virus peaks in the late summer months, and influenza A in April to June. We find significant associations between detection of human parainfluenza 3 and human rhinovirus with the month's mean dew point. Using a cross-wavelet transform we find a significant out-of-phase relationship between human parainfluenza 3 and temperature and dew point.

Conclusions: Our results are important for understanding the temporal risk associated with circulating pathogens in Southern Central Vietnam. Specifically, our results can inform timing of routing seasonal influenza vaccination and for when observed respiratory illness is likely viral, leading to judicious use of antibiotics in the region.
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http://dx.doi.org/10.1016/j.ijid.2018.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7110808PMC
October 2018

Geographical and temporal patterns of rabies post exposure prophylaxis (PEP) incidence in humans in the Mekong River Delta and Southeast Central Coast regions in Vietnam from 2005 to 2015.

PLoS One 2018 10;13(4):e0194943. Epub 2018 Apr 10.

International Livestock Research Institute, Hanoi, Vietnam.

Background: In Vietnam, rabies has been a notifiable disease for more than 40 years. Over the last five years, on average, more than 350,000 people per year have been bitten by dogs and cats while more than 80 human deaths have been reported yearly. No studies have been conducted to evaluate the geographical and temporal patterns of rabies in humans in Vietnam. Therefore, the main objective of this study was to assess the geographical and temporal distributions of rabies post exposure prophylaxis (PEP) incidence in humans in Vietnam from 2005 to 2015.

Methods: Average incidence rabies (AIR) PEP rates for every 3 or 4 years (2005-2008, 2009-2012 and 2013-2015) were calculated to describe the spatial distribution of rabies PEP. Hotspot analysis was implemented to identify patterns of spatial significance using the Getis-Ord Gi statistic. For temporal pattern analysis, two regions [Mekong River Delta (MRD) and Southeast Central Coast (SCC)], with the highest incidence rates, and the seasonal-decomposition procedure based on loess (STL), were compared to assess their temporal patterns of rabies PEP.

Findings: We found hotspots in southern Vietnam and coldspots in northern Vietnam during the study period. Rabies cases were limited to specific areas. In addition, the hotspot analysis showed that new risk areas were identified in each period which were not observed in incidence rate maps. The seasonal plots showed seasonal patterns with a strong peak in February/July and a minor peak in October/December in the MRD region. However, in the SCC, a small peak was detected at the early part of each year and a strong peak in the middle of each year.

Conclusion: Our findings provide insight into understanding the geographical and seasonal patterns of rabies PEP in Vietnam. This study provides evidence to aid policy makers when making decisions and investing resources. Such information may also be utilized to raise public awareness to prevent rabies exposures and reduce unnecessary PEP.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194943PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892892PMC
July 2018

Valine/isoleucine variants drive selective pressure in the VP1 sequence of EV-A71 enteroviruses.

BMC Infect Dis 2017 05 8;17(1):333. Epub 2017 May 8.

Cirad, UMR 17, Intertryp, TA-A17/G, Campus International de Baillarguet, 34398, Montpellier Cedex 5, France.

Background: In 2011-2012, Northern Vietnam experienced its first large scale hand foot and mouth disease (HFMD) epidemic. In 2011, a major HFMD epidemic was also reported in South Vietnam with fatal cases. This 2011-2012 outbreak was the first one to occur in North Vietnam providing grounds to study the etiology, origin and dynamic of the disease. We report here the analysis of the VP1 gene of strains isolated throughout North Vietnam during the 2011-2012 outbreak and before.

Methods: The VP1 gene of 106 EV-A71 isolates from North Vietnam and 2 from Central Vietnam were sequenced. Sequence alignments were analyzed at the nucleic acid and protein level. Gene polymorphism was also analyzed. A Factorial Correspondence Analysis was performed to correlate amino acid mutations with clinical parameters.

Results: The sequences were distributed into four phylogenetic clusters. Three clusters corresponded to the subgenogroup C4 and the last one corresponded to the subgenogroup C5. Each cluster displayed different polymorphism characteristics. Proteins were highly conserved but three sites bearing only Isoleucine (I) or Valine (V) were characterized. The isoleucine/valine variability matched the clusters. Spatiotemporal analysis of the I/V variants showed that all variants which emerged in 2011 and then in 2012 were not the same but were all present in the region prior to the 2011-2012 outbreak. Some correlation was found between certain I/V variants and ethnicity and severity.

Conclusions: The 2011-2012 outbreak was not caused by an exogenous strain coming from South Vietnam or elsewhere but by strains already present and circulating at low level in North Vietnam. However, what triggered the outbreak remains unclear. A selective pressure is applied on I/V variants which matches the genetic clusters. I/V variants were shown on other viruses to correlate with pathogenicity. This should be investigated in EV-A71. I/V variants are an easy and efficient way to survey and identify circulating EV-A71 strains.
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http://dx.doi.org/10.1186/s12879-017-2427-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5422960PMC
May 2017

Exposure to paternal tobacco smoking increased child hospitalization for lower respiratory infections but not for other diseases in Vietnam.

Sci Rep 2017 03 31;7:45481. Epub 2017 Mar 31.

Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

Exposure to environmental tobacco smoke (ETS) is an important modifiable risk factor for child hospitalization, although its contribution is not well documented in countries where ETS due to maternal tobacco smoking is negligible. We conducted a birth cohort study of 1999 neonates between May 2009 and May 2010 in Nha Trang, Vietnam, to evaluate paternal tobacco smoking as a risk factor for infectious and non-infectious diseases. Hospitalizations during a 24-month observation period were identified using hospital records. The effect of paternal exposure during pregnancy and infancy on infectious disease incidence was evaluated using Poisson regression models. In total, 35.6% of 1624 children who attended follow-up visits required at least one hospitalization by 2 years of age, and the most common reason for hospitalization was lower respiratory tract infection (LRTI). Paternal tobacco smoking independently increased the risk of LRTI 1.76-fold (95% CI: 1.24-2.51) after adjusting for possible confounders but was not associated with any other cause of hospitalization. The population attributable fraction indicated that effective interventions to prevent paternal smoking in the presence of children would reduce LRTI-related hospitalizations by 14.8% in this epidemiological setting.
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http://dx.doi.org/10.1038/srep45481DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5374438PMC
March 2017

Randomized safety and immunogenicity trial of a seasonal trivalent inactivated split virion influenza vaccine (IVACFLU-S) in healthy young Vietnamese adults.

Vaccine 2016 10 24;34(45):5457-5462. Epub 2016 Aug 24.

PATH US, Seattle, WA 98121, United States. Electronic address:

Background: Under the auspices of the World Health Organization (WHO) Global Action Plan, PATH supported evaluation of a trivalent, seasonal inactivated influenza vaccine candidate produced by the Institute of Vaccines and Medical Biologicals (IVAC), a Vietnamese manufacturer.

Methods: In 2015, 60 healthy adult subjects 18-45years of age were enrolled in a Phase 1, single center, double blind, randomized, placebo-controlled study conducted at a district health center in Thai Binh Province, Vietnam. The study evaluated the overall safety and immunogenicity of a seasonal, trivalent inactivated split virion influenza vaccine. Volunteers were given either vaccine or placebo in a randomized 1:1 ratio. After undergoing screening, eligible volunteers provided their signed consent and were enrolled in the study. On the first day of immunization, randomly chosen volunteers received IVACFLU-S 15μg (mcg) hemagglutinin of each of the three strains in 0.5mL or placebo by intramuscular injection. All volunteers were monitored for adverse events and underwent blood testing at screening and Day 8 to assess the vaccine candidate's safety. Sera obtained before and 21days after immunization were tested for influenza antibody titers using the hemagglutination-inhibition (HAI) and microneutralization tests (MNT).

Results: Vaccine was well tolerated, and there were no serious adverse events reported. HAI and MNT identified serum antibody responses against the three influenza strains in nearly all volunteers who received the vaccine. Overall, serum HAI responses of fourfold or greater were observed in 93 percent, 83 percent, and 77 percent of H1, H3, and B strains, respectively. Seroprotection rates were also very high.

Conclusions: IVAC's seasonal, trivalent influenza vaccine was safe and well tolerated and induced high levels of seroconversion and seroprotection rates. These clinical data are a first step towards demonstrating the feasibility of producing the vaccine locally and that seasonal vaccine production in Vietnam may be an effective strategy for enhancing the global influenza vaccine supply. ClinicalTrials.gov number NCT02598089, October 15, 2015.
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http://dx.doi.org/10.1016/j.vaccine.2016.08.052DOI Listing
October 2016

Cost of rotavirus diarrhea for programmatic evaluation of vaccination in Vietnam.

BMC Public Health 2016 08 11;16(1):777. Epub 2016 Aug 11.

National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.

Background: Rotavirus is the most common etiology of diarrhea-associated hospitalizations and clinic visits in Vietnamese children < 5 years old. To estimate the economic burden of rotavirus-associated formal healthcare encounters, an economic study was conducted.

Methods: A cost-of-illness study was performed from a societal perspective. Data were collected from children below the age of five years who presented to a clinic or hospital with symptoms of acute gastroenteritis (AGE). Patient-specific information on resource use and cost was obtained through caregiver interviews and medical chart review. Costs are presented in 2014 US dollar ($).

Results: A total of 557 children with symptoms of AGE were enrolled from March through June 2009, with mean age of 16.5 months. Of the 340 outpatients and 217 admitted patients enrolled, 41 % tested rotavirus positive. It was found that, from a societal perspective, the mean total cost of AGE was $175. Costs of patients with and without rotavirus were $217 and $158, respectively. From multiple regression analysis, it was found that rotavirus infection, patient age and receiving oral rehydration solution before visiting health facility had significant effect on the costs.

Conclusions: This study clearly demonstrated substantial economic burden of AGE including rotavirus disease. They were significantly greater than the previously reported cost estimates in Vietnam. These updated costs of illness result in more favorable vaccine cost-effectiveness than in previous economic evaluations.
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http://dx.doi.org/10.1186/s12889-016-3458-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4982427PMC
August 2016

Population-Based Incidence Rates of First-Ever Stroke in Central Vietnam.

PLoS One 2016 11;11(8):e0160665. Epub 2016 Aug 11.

Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University Graduate School of Biomedical Sciences, Sakamoto, Nagasaki, Japan.

Introduction: Stroke incidence data with methodologically acceptable design in Southeast Asia countries is limited. This study aimed to determine incidence of age-, sex- and subtype-specific first-ever stroke (FES) in Vietnam.

Methods: We conducted a hospital-based retrospective study, targeting all stroke cases hospitalized at a solo-provider hospital in our study site of Nha Trang from January 2009 to December 2011 with International Classification of Diseases, 10th revision (ICD-10) codes I60-69. We calculated positive predictive values (PPVs) of each ICD-10-coded stroke by conducting a detailed case review of 190 randomly selected admissions with ICD-10 codes of I60-I69. These PPVs were then used to estimate annual incident stroke cases from the computerized database. National census data in 2009 was used as a denominator.

Results: 2,693 eligible admissions were recorded during the study period. The crude annual incidence rate of total FES was 90.2 per 100,000 population (95% CI 81.1-100.2). The age-adjusted incidence of FES was 115.7 (95% CI 95.9-139.1) when adjusted to the WHO world populations. Importantly, age-adjusted intracerebral hemorrhage was as much as one third of total FES: 36.9 (95% CI 26.1-51.0).

Conclusions: We found a considerable proportion of FES in Vietnam to be attributable to intracerebral hemorrhage, which is as high or exceeding levels seen in high-income countries. A high prevalence of improperly treated hypertension in Vietnam may underlie the high prevalence of intracerebral hemorrhagic stroke in this population.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0160665PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4981455PMC
July 2017

Seasonality of absolute humidity explains seasonality of influenza-like illness in Vietnam.

Epidemics 2015 Dec 28;13:65-73. Epub 2015 Aug 28.

Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Hanoi, Viet Nam; Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.

Background: Experimental and ecological studies have shown the role of climatic factors in driving the epidemiology of influenza. In particular, low absolute humidity (AH) has been shown to increase influenza virus transmissibility and has been identified to explain the onset of epidemics in temperate regions. Here, we aim to study the potential climatic drivers of influenza-like illness (ILI) epidemiology in Vietnam, a tropical country characterized by a high diversity of climates. We specifically focus on quantifying and explaining the seasonality of ILI.

Methods: We used 18 years (1993-2010) of monthly ILI notifications aggregated by province (52) and monthly climatic variables (minimum, mean, maximum temperatures, absolute and relative humidities, rainfall and hours of sunshine) from 67 weather stations across Vietnam. Seasonalities were quantified from global wavelet spectra, using the value of the power at the period of 1 year as a measure of the intensity of seasonality. The 7 climatic time series were characterized by 534 summary statistics which were entered into a regression tree to identify factors associated with the seasonality of AH. Results were extrapolated to the global scale using simulated climatic times series from the NCEP/NCAR project.

Results: The intensity of ILI seasonality in Vietnam is best explained by the intensity of AH seasonality. We find that ILI seasonality is weak in provinces experiencing weak seasonal fluctuations in AH (annual power <17.6), whereas ILI seasonality is strongest in provinces with pronounced AH seasonality (power >17.6). In Vietnam, AH and ILI are positively correlated.

Conclusions: Our results identify a role for AH in driving the epidemiology of ILI in a tropical setting. However, in contrast to temperate regions, high rather than low AH is associated with increased ILI activity. Fluctuation in AH may be the climate factor that underlies and unifies the seasonality of ILI in both temperate and tropical regions. Alternatively, the mechanism of action of AH on disease transmission may be different in cold-dry versus hot-humid settings.
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http://dx.doi.org/10.1016/j.epidem.2015.06.002DOI Listing
December 2015

A Multi-country Study of the Household Willingness-to-Pay for Dengue Vaccines: Household Surveys in Vietnam, Thailand, and Colombia.

PLoS Negl Trop Dis 2015 1;9(6):e0003810. Epub 2015 Jun 1.

International Vaccine Institute, Seoul, South Korea.

Background: The rise in dengue fever cases and the absence of dengue vaccines will likely cause governments to consider various types of effective means for controlling the disease. Given strong public interests in potential dengue vaccines, it is essential to understand the private economic benefits of dengue vaccines for accelerated introduction of vaccines into the public sector program and private markets of high-risk countries.

Methodology/principal Findings: A contingent valuation study for a hypothetical dengue vaccine was administered to 400 households in a multi-country setting: Vietnam, Thailand, and Colombia. All respondents received a description of the hypothetical dengue vaccine scenarios of 70% or 95% effectiveness for 10 or 30 years with a three dose series. Five price points were determined after pilot tests in order to reflect different local situations such as household income levels and general perceptions towards dengue fever. We adopted either Poisson or negative binomial regression models to calculate average willingness-to-pay (WTP), as well as median WTP. We found that there is a significant demand for dengue vaccines. The parametric median WTP is $26.4 ($8.8 per dose) in Vietnam, $70.3 ($23.4 per dose) in Thailand, and $23 ($7.7 per dose) in Colombia. Our study also suggests that respondents place more value on vaccinating young children than school age children and adults.

Conclusions/significance: Knowing that dengue vaccines are not yet available, our study provides critical information to both public and private sectors. The study results can be used to ensure broad coverage with an affordable price and incorporated into cost benefit analyses, which can inform prioritization of alternative health interventions at the national level.
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http://dx.doi.org/10.1371/journal.pntd.0003810DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4452082PMC
March 2016

Vaccine safety monitoring systems in developing countries: an example of the Vietnam model.

Curr Drug Saf 2015 ;10(1):60-7

Johns Hopk ins Bloomberg School of Public Health, 615 N. Wolfe Street / E5543, Baltimore, Maryland 21205, USA.

Only few health intervention programs have been as successful as vaccination programs with respect to preventing morbidity and mortality in developing countries. However, the success of a vaccination program is threatened by rumors and misunderstanding about the risks of vaccines. It is short-sighted to plan the introduction of vaccines into developing countries unless effective vaccine safety monitoring systems are in place. Such systems that track adverse events following immunization (AEFI) is currently lacking in most developing countries. Therefore, any rumor may affect the entire vaccination program. Public health authorities should implement the safety monitoring system of vaccines, and disseminate safety issues in a proactive mode. Effective safety surveillance systems should allow for the conduct of both traditional and alternative epidemiologic studies through the use of prospective data sets. The vaccine safety data link implemented in Vietnam in mid-2002 indicates that it is feasible to establish a vaccine safety monitoring system for the communication of vaccine safety in developing countries. The data link provided the investigators an opportunity to evaluate AEFI related to measles vaccine. Implementing such vaccine safety monitoring system is useful in all developing countries. The system should be able to make objective and clear communication regarding safety issues of vaccines, and the data should be reported to the public on a regular basis for maintaining their confidence in vaccination programs.
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http://dx.doi.org/10.2174/157488631001150407110644DOI Listing
January 2016

Early indication for a reduced burden of radiologically confirmed pneumonia in children following the introduction of routine vaccination against Haemophilus influenzae type b in Nha Trang, Vietnam.

Vaccine 2014 Dec 1;32(51):6963-6970. Epub 2014 Nov 1.

Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.

Introduction: Despite the global success of Hib vaccination in reducing disease and mortality, uncertainty about the disease burden and the potential impact of Hib vaccination in Southeast Asia has delayed the introduction of vaccination in some countries in the region. Hib vaccination was introduced throughout Vietnam in July 2010 without catch-up. In an observational, population based surveillance study we estimated the impact of routine Hib vaccination on all cause radiologically confirmed childhood pneumonia in Nha Trang, Vietnam.

Materials And Methods: In 2007 active hospital based surveillance was established in Khanh Hoa General Hospital, the only hospital in Nha Trang, Khanh Hoa province. Nasopharyngeal samples and chest radiographs are taken routinely from all children diagnosed with acute respiratory illness on admission. For admissions between 02/2007 and 03/2012 chest radiographs were interpreted for the presence of WHO primary endpoint pneumonia and nasopharyngeal swabs were analysed by PCR for the presence of Influenza A or B, RSV and rhinovirus. We employed Poisson regression to estimate the impact of Hib vaccination on radiologically confirmed pneumonia (RCP) while statistically accounting for potential differences in viral circulation in the post vaccination era which could have biased the estimate.

Results: Of 3151 cases admitted during the study period, 166 had RCP and major viruses were detected in 1601. The adjusted annual incidence of RCP in children younger than 5 years declined by 39% (12-58%) after introduction of Hib vaccination. This decline was most pronounced in children less than 2 years old, adjusted IRR: 0.52 (0.33-0.81), and no significant impact was observed in the 2-4 years old who were not eligible for vaccination, adjusted IRR: 0.96 (0.52-1.72).

Discussion: We present early evidence that the burden of Hib associated RCP in Nha Trang before vaccination was substantial and that shortly after introduction to the routine childhood immunisation scheme vaccination has substantially reduced that burden.
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http://dx.doi.org/10.1016/j.vaccine.2014.10.055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7125610PMC
December 2014

Population based cohort study for pediatric infectious diseases research in Vietnam.

Trop Med Health 2014 Jun;42(2 Suppl):47-58

Institute of Tropical Medicine, Nagasaki University , 1-12-4, Sakamoto, Nagasaki 852-8523, Japan.

A population-based cohort study on pediatric infectious diseases was established at Khanh Hoa Province, central Vietnam in 2006, to determine the etiology and risk factors for severe pediatric infectious diseases (SPID) such as acute respiratory infection (ARI), diarrhea and dengue which are the major causes of under 5 mortality. A population census survey was conducted in Nha-Trang and Ninh-Hoa to collect demographic, social-behavioral data and disease burden on SPID. The study site covered a population of 353,525 residing in 75,826 households with 24,781 children less than 5 years. Hospital databases from two hospitals covering the region were obtained. Linking the census and hospital databases, we were able to investigate on a variety of SPID such as environmental tobacco smoking exposure and increased risked of pediatric pneumonia hospitalization, population density, water supply and risk of dengue fever and animal livestock and risk of hospitalized diarrhea. To determine incidence, viral etiology and risk factors for pediatric ARI/pneumonia, we setup a population based prospective hospitalized Pediatric ARI surveillance at Khanh Hoa General Hospital, Nha-Trang in February 2007. The study has revealed RSV, rhinovirus and influenza A as major viral pathogens, role of multiple viral infection and its interaction with bacteria in the development of pneumonia. In addition, we are also conducting a birth cohort study to investigate the incidence of congenital infection and its impact on physical-neurological development, and role of host genetic polymorphism on SPID hospitalization in Vietnam. Population mobility, high cost of regular census update and low mortality are the challenges.
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http://dx.doi.org/10.2149/tmh.2014-S07DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4204059PMC
June 2014

Oral cholera vaccine development and use in Vietnam.

PLoS Med 2014 Sep 2;11(9):e1001712. Epub 2014 Sep 2.

Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.

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http://dx.doi.org/10.1371/journal.pmed.1001712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4151976PMC
September 2014

Epidemiology, clinical manifestations, and outcomes of Streptococcus suis infection in humans.

Emerg Infect Dis 2014 Jul;20(7):1105-14

Streptococcus suis, a bacterium that affects pigs, is a neglected pathogen that causes systemic disease in humans. We conducted a systematic review and meta-analysis to summarize global estimates of the epidemiology, clinical characteristics, and outcomes of this zoonosis. We searched main literature databases for all studies through December 2012 using the search term "streptococcus suis." The prevalence of S. suis infection is highest in Asia; the primary risk factors are occupational exposure and eating of contaminated food. The pooled proportions of case-patients with pig-related occupations and history of eating high-risk food were 38.1% and 37.3%, respectively. The main clinical syndrome was meningitis (pooled rate 68.0%), followed by sepsis, arthritis, endocarditis, and endophthalmitis. The pooled case-fatality rate was 12.8%. Sequelae included hearing loss (39.1%) and vestibular dysfunction (22.7%). Our analysis identified gaps in the literature, particularly in assessing risk factors and sequelae of this infection.
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http://dx.doi.org/10.3201/eid2007.131594DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4073838PMC
July 2014

Influenza seasonality and vaccination timing in tropical and subtropical areas of southern and south-eastern Asia.

Bull World Health Organ 2014 May 24;92(5):318-30. Epub 2014 Feb 24.

National Institute of Virology, Pune, India .

Objective: To characterize influenza seasonality and identify the best time of the year for vaccination against influenza in tropical and subtropical countries of southern and south-eastern Asia that lie north of the equator.

Methods: Weekly influenza surveillance data for 2006 to 2011 were obtained from Bangladesh, Cambodia, India, Indonesia, the Lao People's Democratic Republic, Malaysia, the Philippines, Singapore, Thailand and Viet Nam. Weekly rates of influenza activity were based on the percentage of all nasopharyngeal samples collected during the year that tested positive for influenza virus or viral nucleic acid on any given week. Monthly positivity rates were then calculated to define annual peaks of influenza activity in each country and across countries.

Findings: Influenza activity peaked between June/July and October in seven countries, three of which showed a second peak in December to February. Countries closer to the equator had year-round circulation without discrete peaks. Viral types and subtypes varied from year to year but not across countries in a given year. The cumulative proportion of specimens that tested positive from June to November was > 60% in Bangladesh, Cambodia, India, the Lao People's Democratic Republic, the Philippines, Thailand and Viet Nam. Thus, these tropical and subtropical countries exhibited earlier influenza activity peaks than temperate climate countries north of the equator.

Conclusion: Most southern and south-eastern Asian countries lying north of the equator should consider vaccinating against influenza from April to June; countries near the equator without a distinct peak in influenza activity can base vaccination timing on local factors.
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http://dx.doi.org/10.2471/BLT.13.124412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4007122PMC
May 2014

Socio-ecological risk factors for prime-age adult death in two coastal areas of Vietnam.

PLoS One 2014 26;9(2):e89780. Epub 2014 Feb 26.

International Vaccine Institute, SNU Research Park, Nakseongdae-dong, Gwanak-gu, Seoul, Korea.

Background: Hierarchical spatial models enable the geographic and ecological analysis of health data thereby providing useful information for designing effective health interventions. In this study, we used a Bayesian hierarchical spatial model to evaluate mortality data in Vietnam. The model enabled identification of socio-ecological risk factors and generation of risk maps to better understand the causes and geographic implications of prime-age (15 to less than 45 years) adult death.

Methods And Findings: The study was conducted in two sites: Nha Trang and Hue in Vietnam. The study areas were split into 500×500 meter cells to define neighborhoods. We first extracted socio-demographic data from population databases of the two sites, and then aggregated the data by neighborhood. We used spatial hierarchical model that borrows strength from neighbors for evaluating risk factors and for creating spatially smoothed risk map after adjusting for neighborhood level covariates. The Markov chain Monte Carlo procedure was used to estimate the parameters. Male mortality was more than twice the female mortality. The rates also varied by age and sex. The most frequent cause of mortality was traffic accidents and drowning for men and traffic accidents and suicide for women. Lower education of household heads in the neighborhood was an important risk factor for increased mortality. The mortality was highly variable in space and the socio-ecological risk factors are sensitive to study site and sex.

Conclusion: Our study suggests that lower education of the household head is an important predictor for prime age adult mortality. Variability in socio-ecological risk factors and in risk areas by sex make it challenging to design appropriate intervention strategies aimed at decreasing prime-age adult deaths in Vietnam.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0089780PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3935940PMC
January 2015

A High Incidence of Intussusception Revealed by a Retrospective Hospital-Based Study in Nha Trang, Vietnam between 2009 and 2011.

Trop Med Health 2013 Sep 20;41(3):121-7. Epub 2013 Aug 20.

Department of Molecular Microbiology and Immunology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan ; Department of Epidemiology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.

Rotavirus is a leading cause of severe diarrhea among children worldwide. Thus, the World Health Organization recommended including rotavirus vaccines in national immunization programs. One concern about rotavirus vaccine, however, is a possible association with intussusception. Thus, it is crucial to know the baseline incidence of intussusception in the first year of life. A study conducted in Hanoi, Vietnam showed that the incidence of intussusception was the highest in the world. This retrospective cross-sectional study was undertaken to determine the incidence of intussusception among children <5 years of age in Nha Trang, Vietnam. Hospital charts between 2009 and 2011 were reviewed in Khanh Hoa Provincial General Hospital where virtually all cases of intussusception occurring in the city were assumed to have been encountered. The incidence of intussusception among children <1 year of age was 296 per 100,000 person-years (95% confidence interval [CI]: 225-382), and that among children <5 years of age was 196 per 100,000 person-years (95% CI: 169-226), confirming the high incidence of intussusception in Vietnam. Nevertheless, there was no intussusception in the first three months of life. We therefore recommend that the first dose of any rotavirus vaccine be administered to infants between 6 and 12 weeks of age.
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http://dx.doi.org/10.2149/tmh.2013-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3801156PMC
September 2013

Seroprevalence of rubella in the cord blood of pregnant women and congenital rubella incidence in Nha Trang, Vietnam.

Vaccine 2014 Feb 7;32(10):1192-8. Epub 2013 Sep 7.

Department of Molecular Microbiology and Immunology, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan. Electronic address:

To investigate susceptibility to and factors associated with rubella infection among pregnant mothers and to estimate the burden of congenital rubella infection (CRI) in Vietnam where rubella-containing vaccine (RCV) is not included in the routine immunization program, we conducted a prospective cohort study in Nha Trang, Vietnam between 2009 and 2010. Rubella-specific immunoglobulin-M and immunoglobulin-G were investigated in cord blood samples by enzyme immunoassay. Corresponding clinical-epidemiological data were analyzed and the national congenital rubella syndrome (CRS) incidence was estimated using modeling. We enrolled 1988 pairs of mothers aged 17-45 years and their newborn babies. No mothers had received RCV. Multivariate analysis revealed that mothers aged 17-24 (aOR 2.5, 95% CI: 1.7-3.8) or 25-34 (1.4, 1.0-2.1) years were more likely to be susceptible than those aged 35-45 years. Overall 28.9% (574/1988, 95% CI: 26.9-30.9%) of mothers were seronegative. The CRI rate was 151 (95% CI: 0-322) per 100,000 live births. Modeling estimated that 3788 babies (95% CI: 3283-4143) were born with CRS annually in Vietnam with an overall CRS incidence of 234 (95% CI: 207-262) cases per 100,000 live births. A substantial proportion of women of childbearing age (WCBA) are at risk of rubella infection during pregnancy and this can result in a high frequency of miscarriage or burden of CRS across Vietnam. Prompt introduction of RCV into national immunization program with catch-up vaccination to children and WCBA will reduce CRI in Vietnam.
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http://dx.doi.org/10.1016/j.vaccine.2013.08.076DOI Listing
February 2014

Immunogenicity of quadrivalent HPV vaccine among girls 11 to 13 Years of age vaccinated using alternative dosing schedules: results 29 to 32 months after third dose.

J Infect Dis 2013 Oct 30;208(8):1325-34. Epub 2013 Jul 30.

PATH, Seattle, Washington.

Background:  Immune response to quadrivalent human papillomavirus (HPV) vaccine delivered at 0, 2, and 6 months in young adolescent females plateaus around 24 months after immunization. Antibody levels >24 months postvaccination using extended dosing schedules is unknown.

Methods:  We conducted a follow-up immunogenicity study of adolescent girls in Vietnam who participated in a noninferiority trial to investigate whether immune responses using 3 alternative dosing schedules (0, 3, 9 months; 0, 6, 12 months; or 0, 12, 24 months) are noninferior to the standard schedule at >2 years after immunization.

Results:  Quadrivalent HPV vaccine immunogenicity delivered on 3 alternative dosing schedules was noninferior for types 6, 11, 16, and 18 at 32 months post-dose 3 compared to the standard schedule. Pre-dose 3 antibody levels for the 0, 12, 24 month schedule were similar to those measured 32-months post-dose 3.

Conclusions:  We found similar antibody concentrations ≥29 months after 3 doses of HPV vaccine regardless of dose-timing, and extended schedules do not produce inferior immune responses. Our findings also suggested that 2 doses of HPV vaccine delivered at 0 and 12 months might afford similar protection. Evidence supporting dosing flexibility could be important for national HPV vaccination policies.
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http://dx.doi.org/10.1093/infdis/jit363DOI Listing
October 2013

A dose-escalation safety and immunogenicity study of a new live attenuated human rotavirus vaccine (Rotavin-M1) in Vietnamese children.

Vaccine 2012 Apr;30 Suppl 1:A114-21

The National Institute of Hygiene and Epidemiology, Hanoi, Viet Nam.

We tested a candidate live, oral, rotavirus vaccine (Rotavin-M1™) derived from an attenuated G1P [8] strain (KH0118-2003) isolated from a child in Vietnam. The vaccine was tested first for safety in 29 healthy adults. When deemed safe, it was further tested for safety and immunogenicity in 160 infants (4 groups) aged 6-12 weeks in a dose and schedule ranging study. The vaccine was administered in low titer (10(6.0)FFU/dose) on a 2-dose schedule given 2 months apart (Group 2L) and on a 3-dose schedule given 1 month apart (Group 3L) and in high titer (10(6.3)FFU/dose) in 2 doses 2 months apart (Group 2H) and in 3 doses 1 month apart (Group 3H). For comparison, 40 children (group Rotarix™) were given 2 doses of the lyophilized Rotarix™ vaccine (10(6.5)CCID(50)/dose) 1 month apart. All infants were followed for 30 days after each dose for clinical adverse events including diarrhea, vomiting, fever, abdominal pain, irritability and intussusception. Immunogenicity was assessed by IgA seroconversion and viral shedding was monitored for 7 days after administration of each dose. Two doses of Rotavin-M1 (10(6.3)FFU/dose) were well tolerated in adults. Among infants (average 8 weeks of age at enrollment), administration of Rotavin-M1 was safe and did not lead to an increased rate of fever, diarrhea, vomiting or irritability compared to Rotarix™, indicating that the candidate vaccine virus had been fully attenuated by serial passages. No elevation of levels of serum transaminase, blood urea, or blood cell counts were observed. The highest rotavirus IgA seroconversion rate (73%, 95%CI (58-88%)) was achieved in group 2H (2 doses--10(6.3)FFU/dose, 2 months apart). The 2 dose schedules performed slightly better than the 3 dose schedules and the higher titer doses performed slightly better than the lower titer doses. These rates of seroconversion were similar to that of the Rotarix™ group (58%, 95%CI (42-73%)). However more infants who received Rotarix™ (65%) shed virus in their stool after the first dose than those who received Rotavin-M1 (44-48%) (p<0.05) and the percent shedding decreased after subsequent doses of either vaccine. Rotavin-M1 vaccine is safe and immunogenic in Vietnamese infants. A trial in progress will assess the safety, immunogenicity and efficacy of Rotavin-M1 (2 doses at 10(6.3)FFU/dose) in a larger number of infants. The trial registration numbers are NCT01375907 and NCT01377571.
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http://dx.doi.org/10.1016/j.vaccine.2011.07.118DOI Listing
April 2012

Immunogenicity of the pentavalent rotavirus vaccine among infants in two developing countries in Asia, Bangladesh and Vietnam.

Vaccine 2012 Apr;30 Suppl 1:A106-13

International Vaccine Institute, Seoul, South Korea.

Background: We evaluated the immunogenicity of the pentavalent rotavirus vaccine (PRV) in two GAVI-eligible Asian countries, Bangladesh and Vietnam, nested in a larger randomized, double-blind, placebo-controlled efficacy trial conducted over a two-year period from 2007 through 2009.

Methods: 2036 infants were randomly assigned, in a 1:1 ratio, to receive three oral doses of PRV or placebo approximately at 6, 10, and 14 weeks of age. Concomitant use of EPI vaccines, including oral poliovirus vaccine (OPV) and diphtheria-tetanus-whole cell pertussis (DTwP) vaccine, was encouraged in accordance to the local EPI schedule. A total of 303 infants were evaluated for immunogenicity and blood samples were collected before the first dose (pD1) and approximately 14 days following the third dose (PD3). The seroresponse rates (≥3-fold rise from pD1 to PD3) and geometric mean titers (GMTs) were measured for anti-rotavirus immunoglobulin A (IgA) and serum neutralizing antibody (SNA) to human rotavirus serotypes G1, G2, G3, G4, and P1A[8], respectively.

Results: Nearly 88% of the subjects showed a ≥3-fold increase in serum anti-rotavirus IgA response in the analysis of the two countries combined. When analyzed separately, the IgA response was lower in Bangladeshi children (78.1% [95% CI: 66.0, 87.5]) than in Vietnamese children (97.0% [95% CI: 89.6, 99.6]), with a PD3 GMT of 29.1 (units/mL) and 158.5 (units/mL), respectively. In the combined population, the SNA responses to the individual serotypes tested ranged from 10 (G3) to 50 (G1) percentage points lower than the responses shown in the developed countries. However, the SNA response to G3 in Vietnamese subjects was 37.3% (95% CI: 25.8, 50.0), which was similar to the G3 response rate in developed countries.

Conclusions: Three oral doses of PRV were immunogenic in two GAVI-eligible Asian countries: Bangladesh and Vietnam. The GMTs of both the serum anti-rotavirus IgA and SNA responses were generally higher in Vietnamese than in Bangladeshi children. The SNA responses varied by individual serotypes and were lower than the results from developed countries. The clinical significance of these observations is not understood because an immune correlate of protection has not been established.
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http://dx.doi.org/10.1016/j.vaccine.2011.11.091DOI Listing
April 2012

Animal livestock and the risk of hospitalized diarrhoea in children under 5 years in Vietnam.

Trop Med Int Health 2012 May 16;17(5):613-21. Epub 2012 Mar 16.

National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.

Objective: To investigate the association between environmental exposure to livestock and incidence of diarrhoea among Vietnamese children.

Methods: A population-based cohort of 353,525 individuals, living in 75,828 households in Khanh Hoa Province, Vietnam, with baseline data covering geo-referenced information on demography, socio-economic status and household animals was investigated. Geographic information system was applied to calculate the density of livestock. The data were linked to hospitalized diarrhoea cases of children under 5 years recorded at two hospitals treating patients from the area as inpatients in the study area.

Results: Overall, 3116 children with diarrhoea were hospitalized during the study period. The incidence of diarrhoea hospitalization was 60.8/1000 child-years. Male gender, age <2 years, higher number of household members and lack of tap water were significantly associated with an increased risk of diarrhoea. There was no evidence that ownership of livestock increased the risk of diarrhoea. In spatial analysis, we found no evidence that a high density of any animals was associated with an increased risk of diarrhoea.

Conclusions: Exposure to animals near or in households does not seem to constitute a major risk for diarrhoea in children under the age of 5 in Vietnam. Public health interventions to reduce childhood diarrhoea burden should focus on well-recognized causes such as sanitation, personal hygiene, access to adequate clean water supply and vaccination.
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http://dx.doi.org/10.1111/j.1365-3156.2012.02969.xDOI Listing
May 2012