Clinical Trials of Quadrivalent Influenza Vaccine

Overall design:

Adopting a randomized, blinded research design. This experiment adopts a seamless connection design of Phase I/II, conducted in two stages: Phase I and Phase II. Phase I is the age/dose escalation stage, and Phase II is the dose extension stage.

Age/dose escalation stage: A randomized, blinded, placebo-controlled study design was used. 120 subjects were enrolled in the study, in order of age from 18 to 49 years old to 50 years old and above, from low dose to high dose. They were divided into four cohorts, with 30 subjects in each cohort (including 20 who received high-dose or low-dose experimental vaccines and 10 who received placebo). The first 6 subjects in each cohort were assigned to be sentinel group, and the researchers reviewed the safety data of the sentinel group within 7 days after vaccination. After confirming safety (not meeting the criteria for suspending/terminating the trial), the remaining 24 subjects in the cohort were enrolled.

Dose expansion stage: A randomized, blinded, positive controlled study design was used. 500 subjects were enrolled, divided into two age groups: 18-49 years old and 50 years old and above. 250 subjects were enrolled in each age group and randomly divided into low-dose group, high-dose group, and positive control group according to a 2:2:1 ratio. The proportion of people aged 60 and above in the population aged 50 and above shall not be less than 80%, and the proportion of people aged 70 and above shall not be less than 30%.