Baseline characteristics of the participants
In this study, 904 subjects who received two doses of inactivated vaccine 6 months prior were assigned to 4 groups for booster vaccination (Trial profile.Baseline characteristics of the participants.Data are n (%) or median. Seropositivity for neutralizing antibody against SARS-CoV-2 from a subset of participants in each group before receiving a booster vaccination at day 0 is defined as a detectable neutralizing antibody titer ≥ 1:30.