N Engl J Med 2021 Jan 13. Epub 2021 Jan 13.
From Janssen Vaccines and Prevention, Leiden, the Netherlands (J. Sadoff, M.L.G., G. Shukarev, A.M.G., J. Stoop, S.T., E.C., G. Scheper, J. Hendriks, M.D., J.V.H., H.S.); Janssen Research and Development, Beerse (D.H., C.T., F.S.), Janssen Clinical Pharmacology Unit, Merksem (W.V.D.), the Center for Vaccinology, Ghent University, Gent (I.L.-R.), SGS Life Sciences (P.-J.B.) and the Center for the Evaluation of Vaccination, University of Antwerp (P.V.D.), Antwerp, and the Center for Clinical Pharmacology, University Hospitals Leuven, Leuven (J. de Hoon) - all in Belgium; Optimal Research, Melbourne, FL (M.K.); the Alliance for Multispecialty Research, Knoxville, TN (W.S.); the Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Boston (K.E.S., D.H.B.); and the Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle (S.C.D.R., K.W.C., M.J.M.).
Background: Efficacious vaccines are urgently needed to contain the ongoing coronavirus disease 2019 (Covid-19) pandemic of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A candidate vaccine, Ad26.COV2.S, is a recombinant, replication-incompetent adenovirus serotype 26 (Ad26) vector encoding a full-length and stabilized SARS-CoV-2 spike protein.
Methods: In this multicenter, placebo-controlled, phase 1-2a trial, we randomly assigned healthy adults between the ages of 18 and 55 years (cohort 1) and those 65 years of age or older (cohort 3) to receive the Ad26.COV2.S vaccine at a dose of 5×10 viral particles (low dose) or 1×10 viral particles (high dose) per milliliter or placebo in a single-dose or two-dose schedule. Longer-term data comparing a single-dose regimen with a two-dose regimen are being collected in cohort 2; those results are not reported here. The primary end points were the safety and reactogenicity of each dose schedule.
Results: After the administration of the first vaccine dose in 805 participants in cohorts 1 and 3 and after the second dose in cohort 1, the most frequent solicited adverse events were fatigue, headache, myalgia, and injection-site pain. The most frequent systemic adverse event was fever. Systemic adverse events were less common in cohort 3 than in cohort 1 and in those who received the low vaccine dose than in those who received the high dose. Reactogenicity was lower after the second dose. Neutralizing-antibody titers against wild-type virus were detected in 90% or more of all participants on day 29 after the first vaccine dose (geometric mean titer [GMT], 224 to 354) and reached 100% by day 57 with a further increase in titers (GMT, 288 to 488), regardless of vaccine dose or age group. Titers remained stable until at least day 71. A second dose provided an increase in the titer by a factor of 2.6 to 2.9 (GMT, 827 to 1266). Spike-binding antibody responses were similar to neutralizing-antibody responses. On day 14, CD4+ T-cell responses were detected in 76 to 83% of the participants in cohort 1 and in 60 to 67% of those in cohort 3, with a clear skewing toward type 1 helper T cells. CD8+ T-cell responses were robust overall but lower in cohort 3.
Conclusions: The safety and immunogenicity profiles of Ad26.COV2.S support further development of this vaccine candidate. (Funded by Johnson & Johnson and the Biomedical Advanced Research and Development Authority of the Department of Health and Human Services; COV1001 ClinicalTrials.gov number, NCT04436276.).