Safety and immunogenicity of a heptavalent pneumococcal conjugate vaccine in infants

Objective: To evaluate the safety and immunogenicity of two lots of a heptavalent Streptococcus pneumoniae conjugate vaccine (PCV) containing seven capsular polysaccharide serotypes (4, 6B, 9V, 14, 18C, 19F, and 23F) conjugated to the outer membrane complex of Neisseria meningitidis serogroup B (OMPC) and administered to infants at 2, 4, 6, and 12 months of age. Methods: One hundred twenty infants were randomly assigned to concurrently receive PCV-OMPC and one of two Haemophilus influenzae type b (Hib) conjugate-DTwP combination vaccines: (1) Hib with a heterologous protein carrier (CRM197, TETRAMUNE(R), Group 1) or (2) an experimental Hib-hepatitis b combination vaccine with the homologous carrier (OMPC, Group 2). All infants in Groups I and 2 received PCV-OMPC (lot 1) at 12 months of age. Another separate group of 120 infants (Group 3) received a different lot of PCV-OMPC concurrently with Hib-CRM197 (TETRAMUNE(R)) at 2, 4, and 6 months of age and then were randomized to receive either PCV-OMPC or a 23-valent polysaccharide (PS) pneumococcal vaccine at 12 months of age. Results: Each PCV-OMPC lot was generally well tolerated and no vaccine-related serious adverse events were reported. Following the primary series, serotype-specific anti-pneumococcal geometric mean concentrations (GMC) were highest for serotypes 1.4, 19F, and 4 and lowest for serotypes 6B and 23F. GMC and seroconversion rates in Group 3 (lot 2) were lower than in Group I (lot 1) for serotypes 613, 14, 18C, and 23F. Antibody responses to serotypes 613, 14, and 18C were significantly lower in Group 2 compared to Group 1. Following a booster dose of PCV-OMPC at 12 months of age, each lot was immunogenic with at least a 5-10-fold increase in antibody levels, and responses were significantly higher among those who received the PS vaccine. Conclusions: PCV-OMPC is generally safe in infants, displays variable immune response by serotype, and concomitant receipt of Hib vaccine with homologous carrier may impact on its immunogenicity. (C) 2003 Elsevier Science Ltd. All tights reserved.