Safety, immunogenicity, and lot consistency of a 13-valent pneumococcal conjugate vaccine in Chinese children aged 2–5 years: A phase III study

BACKGROUND: Pneumococcal conjugate vaccines have significantly reduced the global morbidity and mortality burdens of pneumococcal disease in children under five years of age, but supply constraints remain. We evaluated the safety, immunogenicity, and lot-to-lot consistency of a tetanus toxoid-conjugated 13-valent pneumococcal conjugate vaccine (PCV13) in Chinese children aged 2-5 years. METHODS: In this randomized, Phase III study, 1800 healthy children aged 2-5 years were enrolled and randomized (1:1:1) to receive a single dose of one of three consecutive manufacturing lots of PCV13. Safety and reactogenicity were assessed up to 30 days post-vaccination, and serious adverse events (SAEs) up to 180 days. Immunogenicity was evaluated 30 days post-vaccination by measuring serotype-specific IgG concentrations using ELISA. The primary objective was to demonstrate lot-to-lot consistency based on predefined equivalence criteria for geometric mean concentration (GMC) ratios; seropositivity and safety outcomes were secondary endpoints. RESULTS: The prespecified primary objective was met: for all 13 vaccine serotypes, pairwise serotype-specific IgG geometric mean ratios (GMRs) between the three manufacturing lots fell within the predefined equivalence margins (0.5-2.0). By Day 30, seropositivity rates (IgG ≥0.35 μg/mL) were ≥ 99% for 12 serotypes and 85.6-88.3% for serotype 3. Solicited local and systemic reactions were predominantly mild or moderate in severity and occurred at similar frequencies across groups; rates of SAEs and unsolicited adverse events considered related to vaccination were low. CONCLUSION: This tetanus toxoid-conjugated PCV13 met prespecified criteria for lot-to-lot manufacturing consistency and showed favorable immunogenicity and safety profiles in children aged 2-5 years, supporting its licensed use in this age group. The vaccine may help strengthen the global supply of pneumococcal conjugate vaccines, particularly in regions with unmet pediatric vaccination needs.