Alliance for Pandemic Preparedness

January 14, 2021

Interim Results of a Phase 1–2a Trial of Ad26.COV2.S Covid-19 Vaccine



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Interim results of a randomized, double-blind, placebo-controlled phase 1-2a trial of the Johnson & Johnson adenovirus vector vaccine Ad26.COV2.S (n=805) showed acceptable safety, reactogenicity, and immunogenicity profiles across age and dose groups. Participants included in the interim analysis were split between “cohort 1” (n=402, age 18-55 years), which received two doses 56 days apart, and “cohort 3” (n=403, age >=65 years), which received only one dose; both cohorts received either alow-dose vaccine, high-dose vaccine, or placebo.

The most frequent solicited adverse events were fatigue, headache, myalgia, and injection-site pain, while the most frequent systematic adverse event was fever that resolved within 1 or 2 days. Adverse events were less common in “cohort 3” than in “cohort 1” and in those receiving low versushigh dose vaccine. Neutralizing-antibody titers were detected in 90% or more of all participants on day 29 after the first dose, and reached 100% by day 57 regardless of age or dose group. A second dose increased titers 2.6 to 2.9 times. On day 14, CD4+ T-cell responses were detected in 76-83% of “cohort 1” participants and in 60-67% of “cohort 3” participants.

Sadoff et al. (Jan 13, 2021). Interim Results of a Phase 1–2a Trial of Ad26.COV2.S Covid-19 Vaccine. New England Journal of Medicine.