Decreased immune response to pneumococcal conjugate vaccine after 23-valent pneumococcal polysaccharide vaccine in children.

BACKGROUND: Pneumococcal polysaccharide vaccine (PPV) is used in children at high risk of IPD. PPV is generally not considered to induce immunologic memory, whereas pneumococcal conjugate vaccines (PCVs) elicit protective antibody responses in infants and induce immunologic memory. Little is known about the characteristics of immune responses to PCV in children who previously received PCV and PPV in series. OBJECTIVE: To characterize immune responses to 13-valent pneumococcal CRM197 conjugate vaccine (PCV13; serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) in children vaccinated in infancy with 9-valent pneumococcal-meningococcal C-CRM197 conjugate combination vaccine (PCV9-MnCC), followed by a toddler dose of PCV9-MnCC or 23-valent pneumococcal polysaccharide vaccine (PPV23). METHODS: Children (n=89) who received PCV9-MnCC in infancy and PPV23 or PCV9-MnCC at age 12 months in a previous (2002-2003) study were vaccinated at age 7.5 years with PCV13; groups PPV23/PCV13 (n=50) and PCV9/PCV13 (n=39). Immunoglobulin (Ig)G antibodies, avidity, and opsonophagocytic activity (OPA) were measured before and at 1 and 4 weeks postvaccination. RESULTS: One week postvaccination, IgG levels increased significantly for all serotypes in both groups, and >97% of vaccinees achieved IgG ≥0.35µg/ml 4 weeks after PCV13 vaccination. The PCV9/PCV13 group had higher IgG responses compared with the PPV23/PCV13 group. The upper limits of the 95% confidence intervals of the PPV23/PCV13:PCV9/PCV13 IgG geometric mean concentration ratios were <1.0 for serotypes 1, 4, 5, 9V, 18C, and 23F at 1 week. OPA and avidity results supported these findings. CONCLUSIONS: PPV23 vaccination of toddlers may compromise subsequent responses to pneumococcal conjugate vaccines. The clinical relevance of this finding is unclear.

Immune response to octavalent diphtheria- and tetanus-conjugated pneumococcal vaccines is serotype- and carrier-specific: the choice for a mixed carrier vaccine.

BACKGROUND: Development of protein-conjugated pneumococcal vaccines for infants has led to formulations that are immunogenic in the age group at highest risk for pneumococcal diseases. This study focuses on the search for an optimal formulation. METHODS: In a randomized trial Icelandic infants (n = 160) were immunized at age 3, 4 and 6 months with one of two octavalent pneumococcal conjugate vaccines (serotypes 3, 4, 6B, 9V, 14, 18C, 19F and 23F conjugated to diphtheria toxoid (PncD) or tetanus protein (PncT) followed with a booster of either the same conjugate or 23-valent polysaccharide vaccine at 13 months. Safety data were collected after each vaccination, and IgG responses (enzyme-linked immunosorbent assay) were measured at 3, 4, 6, 7, 13 and 14 months. RESULTS: Both conjugates were safe and caused fewer local reactions than the routine vaccines (P < 0.0001). At 7 months both groups had significant IgG response to all serotypes. The geometric mean concentration range was 0.35 to 4.09 and 0.65 to 3.38 microg/ml for PncD and PncT, respectively, with 88.2 to 100% and 92.4 to 100% of subjects reaching > or = 0.15 microg/ml. The PncD gave better primary responses to serotypes 3, 9V and 18C, whereas PncT gave better response to serotype 4. Similar responses were induced to the other serotypes. Good booster IgG responses were obtained in all vaccine groups; 97.5 to 100% of subjects reached > or = 1 microg/ml. CONCLUSIONS: Both octavalent pneumococcal conjugates were safe and immunogenic in infants. Based on the results from this and similar trials, a mixed diphtheria and tetanus pneumococcal conjugate vaccine was designed to provide the optimal immune response to each serotype.