Anamnestic immune response in 3- to 4-year-old children previously immunized with 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine as 2-dose or 3-dose priming and a booster dose in the first year of life.

BACKGROUND: Immunogenicity of 10-valent pneumococcal nontypeable Haemophilus influenzae protein d conjugate vaccine (PHiD-CV), administered as 2-dose or 3-dose priming followed by a booster dose, has been described previously. The present study evaluated immunologic memory following PHiD-CV vaccination according to these vaccination schedules. METHODS: A dose of PHiD-CV (to test anamnestic responses) was administered to 172 children at 36 to 46 months of age; 110 of them had previously been vaccinated with PHiD-CV according to 2 + 1 or 3 + 1 schedules (PHiD-CV [2 + 1] and PHiD-CV [3 + 1] groups) and 62 were unprimed age-matched controls. To measure immune responses before and 7 to 10 days after the PHiD-CV dose, 22F-inhibition enzyme-linked immunosorbent assay and opsonophagocytic activity (OPA) assay were used. RESULTS: Serotype-specific IgG geometric mean concentrations (GMCs) and OPA geometric mean titers increased substantially (from before to 7 to 10 days after the additional PHiD-CV dose) for all 10 vaccines and 2 cross-reactive serotypes (6A and 19A) in the children previously vaccinated with PHiD-CV, regardless of the vaccination schedule used. Antibody GMCs and OPA geometric mean titers after the administration of the PHiD-CV dose were markedly higher in both previously PHiD-CV-vaccinated groups than in the unprimed control group, clearly demonstrating prior induction of immunologic memory. Antiprotein D antibody GMCs had also increased substantially from before to 7 to 10 days after vaccination in all 3 groups, with higher antibody GMCs in the previously vaccinated groups than in the control group. CONCLUSION: PHiD-CV vaccination according to 2 + 1 or 3 + 1 schedules resulted in comparable anamnestic immune responses. These findings suggest that similar protective efficacy may be achieved with both the schedules.

Immunogenicity of a 2-dose priming and booster vaccination with the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine.

BACKGROUND: The immunogenicity of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) was determined following a simplified 2-dose priming and the more commonly employed 3-dose priming both followed by a booster dose. METHODS: A total of 351 healthy subjects were primed with PHiD-CV at either 3 and 5 or 3, 4 and 5 months of age followed in all subjects by a booster dose at 11 to 12 months of age. Serotype-specific pneumococcal responses were measured by 22F-inhibition ELISA and opsonophagocytic assays 1 month following primary and booster vaccinations. RESULTS: Depending on the serotype, the percentages of subjects reaching the ELISA antibody threshold of 0.2 microg/mL were 92.8% to 98.0% following 2 primary doses and 96.1% to 100% following 3 primary doses except for serotype 6B (55.7% and 63.1%, respectively) and serotype 23F (69.3% and 77.6%, respectively). Opsonophagocytic activity (OPA) could be measured in 74.4% to 100% and 88.9% to 100% of the subjects after the 2-dose or 3-dose priming, respectively, except for serotype 1 (60.8% and 62.9%, respectively). In both groups, robust increases in ELISA antibodies and OPA titers were observed for all serotypes after the booster dose. Higher postprimary and postbooster ELISA antibody levels and OPA titers were observed for most serotypes following the 3+1 schedule. CONCLUSION: PHiD-CV was immunogenic in both schedules, but further effectiveness data are needed to fully understand the public health benefit to be expected from these schedules in terms of prevention against invasive and mucosal infections.