Association Between Pre-Existing Anti-Diphtheria Toxoid IgG and Immune Responses to a CRM197-Conjugated 14-Valent Pneumococcal Conjugate Vaccine in Infants: A Post Hoc Analysis of a Multicenter Phase III Trial

Background/Objectives: Maternally transferred antibodies protect infants early in life, but high concentrations can reduce immune responses to primary vaccination. CRM197 is a nontoxic mutant of diphtheria toxin that retains antigenic similarity to the native protein. We therefore investigated whether anti-diphtheria antibodies present before vaccination were related to responses against pneumococcal polysaccharides conjugated to CRM197.