Randomization and blinding
Participants were randomly assigned to the homologous or heterologous arms in parallel with equal probability. The balanced block randomization list was generated using the block size of 4 and sample size through the research institute’s web-based software.Trained vaccine administrators enrolled the participants and assigned them to the trial groups according to the randomization list. While maintaining confidentiality, the vaccine administrators loaded the vaccines in a separate cubicle and administered them in the vaccination room. All other team members were blinded to the randomization list, including those responsible for the safety evaluation, collecting information, data analysis, laboratory assessors, and participating patients.