Randomization and blinding
For each subject recruited, the inclusion number was allocated in the chronological order of the subject, which was included in the trial from I-001 to I-180 (for the 9–12-year age group), II-001 to II-180 (for the 13–17-year age group), and III-001 to III-180 (for the 18–40-year age group). The subjects were randomized into treatment groups. The doctor strictly followed the list of randomization provided by Bio Farma. Treatment was allocated in accordance with a randomization list so that each randomization number corresponded to only one strictly randomly assigned treatment group (QIV batch A, QIV batch B, QIV batch C, and TIV).