Phase III Clinical Trial of Recombinant Respiratory Syncytial Virus Vaccine (CHO Cells)

This is a phase III clinical trial with a multicenter, randomized, blinded, placebo-controlled design to evaluate the protective efficacy, safety, and immunogenicity of the recombinant respiratory syncytial virus (RSV) vaccine (CHO cell) in individuals aged 60 and above. Sample Size and Trial Grouping: This trial plans to enroll 25,000 trial participants aged ≥60 years (with approximately 30% aged 70 and above), with a relatively balanced gender distribution. Participants of each age group (60-69 years old, ≥70 years old) will be randomly assigned to the trial group and the placebo group in a 1:1 ratio. The sample size for the immunogenicity subgroup is not calculated based on statistical power. Referring to similar clinical trials of RSV vaccines and in conjunction with the immunogenicity observation objectives of this trial, the first 300 trial participants (including those from both age groups) from each site under the leading institution will be included in the immunogenicity subgroup, for a total of 1,200 participants.