Immunologic considerations for the timing of the booster dose of 7-valent pneumococcal conjugate vaccine in young children.

BACKGROUND: The booster (fourth) dose of 7-valent pneumococcal conjugate vaccine (PCV7) is recommended to be given at 12-15 months but in Canada it better fits the national schedule at 18 months, prompting this comparison of the safety and immunogenicity of booster immunization at 15 or 18 months. METHODS: Children who had completed a study of primary PCV7 immunization (with final serology at 7-8 months of age) were enrolled at 12 months, bled and randomly assigned to receive a PCV7 booster at age 15 or 18 months, with serologic testing before and 4 weeks afterward. Adverse events were documented for 3 days postbooster. Antibody concentrations were measured for the 7 pneumococcal serotypes and Haemophilus influenzae type b at 7-8, 12, 15 or 18 months and after boosting. RESULTS: Three hundred thirty-one children were boosted, 167 at 15 months and 164 at 18 months. Pneumococcal geometric mean antibody concentrations declined by 15 months to 23.4% of peak geometric mean concentrations at age 7-8 months and to 19.8% by 18 months. Spontaneous increases in 1 or more antibody concentrations were noted in 195 subjects (61.7%), most commonly with types 6B and 19F. Antibody responses to PCV7 were similarly brisk at 15 and 18 months. Mild injection-site redness and swelling were significantly more frequent at 15 than 18 months but no other differences in reactogenicity were observed. CONCLUSIONS: Residual antibody concentrations differed minimally between 15 and 18 months. Spontaneous antibody increases often occurred before boosting, possibly from colonization. PCV7 booster vaccination at 18 months appears to be safe and provides comparable immunogenicity to 15 months vaccination.

Assessment of the compatibility of co-administered 7-valent pneumococcal conjugate, DTaP.IPV/PRP-T Hib and hepatitis B vaccines in infants 2-7 months of age.

This study assessed compatibility of concurrently administered 7-valent pneumococcal conjugate (PCV7), hepatitis B (HB) and DTaP.IPV/Hib vaccines. Infants were given DTaP.IPV/Hib and HB at 2, 4, 6 months and randomly assigned (2:1) to receive PCV7 concurrently or sequentially (at 3, 5, 7 months). Antibody levels were compared in 246 concurrent and 122 sequential vaccinees. Responses to PCV7, DTaP.IPV/Hib and HB were generally unaltered with concurrent administration except that Hib responses were increased (p=0.008) and HB responses were reduced (p=0.006) with concurrent dosing, the latter possibly from same thigh injection with DTaP.IPV/Hib. We conclude that PCV7, DTaP.IPV/Hib and HB are compatible with concurrent, separate injections.