Study design and participants
DISEASE, SARS-COV-2 INFECTION, APPENDIX
A single-center, randomized, double-blind, active-controlled, phase III immuno-bridging clinical trial was conducted, aiming to assess the immunogenicity and safety of Omicron vaccine as compared with the authorized prototype vaccine CoronaVac in Jiangsu Province, China. Healthy adults aged 18 years and older, without a history of or current SARS-CoV-2 infection, were eligible for enrolment. Participants should have previously received either 2 or 3 doses of CoronaVac at least 6 months before (2C or 3C cohorts), for which the time intervals were 21-60 days between the first and second doses and at least 6 months between the second and third doses. Within each cohort, enrolled eligible participants were randomly assigned, in a ratio of 2:1, to receive one booster dose of Omicron vaccine (the trial group) or CoronaVac (the control group), and the first 80 participants in the trial group and the first 40 participants in the control group were assigned to the immunogenicity subgroups. Randomization codes were generated by the statistician using stratified block randomization, according to age stratification (18 to 59 years, or ≥60 years; 4:1 ratio). The randomization code was allocated to each participant in the sequence of enrolment order, and then the participants received the investigational products labeled with the same code. Concealed random group allocations and blinding codes were kept in sealed envelopes, and investigators, participants, and laboratory staff were all blinded to the group allocation. Detailed information on the inclusion/exclusion criteria for participants is listed in the Appendix.This trial was approved by the ethics committee of Jiangsu Provincial Centre for Disease Control and Prevention. Written informed consent was obtained from all participants before screening, and the trial was conducted in accordance with the principles of the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use, the standards of Good Clinical Practice, and Chinese regulatory requirements. The trial was registered in the ClinicalTrials.gov registration database with an identifier of NCT05381350.