Infant immunization with pneumococcal CRM197 vaccines: Effect of saccharide size on immunogenicity and interactions with simultaneously administered vaccines

Six pentavalent pneumococcal conjugate vaccines (Pn-CRM197) were evaluated among 400 infants, The vaccines differed in saccharide chain length (oligosaccharide [OS] or polysaccharide [PS]) and saccharide quantity (0.5, 2, or 5 mu g). Subjects were randomized into groups 1-6 (Pn-CRM197 recipients) or 7 (controls) for immunization at 2, 4, and 6 months of age, Pn-CRM197 were well tolerated and elicited mean antibody concentrations that exceeded those in controls for all 5 capsular serotypes, PS formulations were generally more immunogenic than their OS counterparts. For PS vaccines, a dose-response was documented (5 mu g > 2 mu g > 0.5 mu g), but the differences between the 5- and 2-mu g formulations were insignificant. The mean anti-PRP antibody concentration was significantly higher among Pn-CRM197, recipients, It is concluded that PS vaccines are more immunogenic than OS vaccines, The improved immunogenicity from Haemophilus type b oligosaccharide conjugate (HbOC) vaccine when given with Pn-CRM197 suggests that a decreased dose of HbOC vaccine may be sufficient to elicit protection.