Trial Profile
Reasons for unmet inclusion criteria in screened participants are reported in eTable 10 in Of participants who underwent a serologic test on day 0 (cohort 1, 5905; cohort 2, 1975), 35.7% of those in the cohort 1 vaccine group and 33.7% of those in the cohort 2 vaccine group, as well as 36.7% of those in the cohort 1 placebo group and 29.7% in the cohort 2 placebo group, had anti–SARS-CoV-2 S1 IgG (