The purpose of the Phase 1/2 study is to assess the safety, reactogenicity, and immunogenicity of Ad26.COV2.S at 2 dose levels, administered intramuscularly (IM) as a single-dose or 2-dose schedule, with a single booster vaccination administered in one cohort, in healthy adults aged greater than or equal to 18 to less than or equal to 55 years and in adults aged greater than or equal to 65 years in good health with or without stable underlying conditions.
Interim Results
The New England Journal of Medicine published the interim results for this clinical study.
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], 212 to 354), regardless of vaccine dose or age group, and reached 96% by day 57 with a further increase in titers (GMT, 288 to 488) in cohort 1a. 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 15, 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 supports the 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)
