Immunogenicity and Reactogenicity of Pneumococcal Conjugate Vaccines in Infants and Children

Abstract

Several investigational pneumococcal conjugate vaccines (PCVs) have been evaluated in phase II immunogenicity and reactogenicity studies with infants. PCVs prevent mucosal infections (acute otitis media [AOM] and colonization), and thus, some groups have also made efforts to characterize the mucosal immune response after vaccination in the hope of finding serological correlates of mucosal protection. High-avidity antibodies can have greater functional capacity than low-avidity antibodies, and the increase in avidity is regarded as a marker of the development of immunological memory. The South African follow-up study suggests that HIV-infected children would benefit from a booster immunization while non-HIV infected children may have persistent protection due to natural boosting via pneumococcal colonization or cross-reacting antigens. The geometric mean concentrations (GMCs) of antibodies against diphtheria toxoid were generally higher in the group given PCV7-CRM in studies with both wP (15)- and acellular pertussis protein (aP)-containing combinations. In a number of PCV7-CRM trials, the response to a primary series of doses of a diphtheria-tetanus-pertussis combination vaccine (DTP) alone has been compared to the response to DTP coadministered with PCV7-CRM. PCV11-D-T given to infants at 18 weeks of age was able to boost the diphtheria toxoid and TT responses of Filipino infants who had received a DTwP vaccine at 6, 10, and 14 weeks. In a study of PCV11-D-T, a formulation with aluminum hydroxide induced higher GMCs of antibodies, but differences were not statistically significant. In general, there were no significant differences in the avidities of antibodies.