Safety and immunogenicity of the American Academy of Pediatrics-recommended sequential pneumococcal conjugate and polysaccharide vaccine schedule in pediatric solid organ transplant recipients

Objective. Solid organ transplant recipients are at increased risk for invasive pneumococcal disease. The American Academy of Pediatrics recommends immunization with sequential pneumococcal vaccines for this group; however, data are lacking. Accordingly, this study was designed to evaluate the safety and immunogenicity of the recommended regimen. Methods. Pediatric solid organ transplant recipients (n = 25) between 2 and 18 years of age who had not previously received 7-valent conjugate pneumococcal vaccine (PCV7) were enrolled. These patients received 2 doses of the PCV7 and a single dose of the 23-valent polysaccharide pneumococcal vaccine (23V). Each vaccine dose was given 2 months apart. Healthy age-matched controls ( n = 23) were enrolled for comparison. Controls received a single dose of PCV7 followed 2 months later by a single dose of 23V. Antibody concentrations to serotypes 1, 4, 5, 6B, 9V, 14, 18C, 19F, and 23F were measured by enzyme-linked immunosorbent assay prevaccination, 2 months after each vaccine dose and 5 to 7 months after 23V. Local and systemic reactions to each vaccine dose were recorded. Results. Systemic and injection-site reactions were comparable between the 2 groups. Significant rises in serotype-specific pneumococcal antibody geometric mean concentrations from prevaccination levels were observed in both groups; however, final antibody responses to serotypes 1, 4, 9V, 14, 18C, 19F, and 23F were significantly lower in solid organ transplant recipients compared with the control group. Antibody concentrations did not increase significantly among solid organ transplant patients after the second dose of PCV7. No additional increase in PCV7-associated serotype-specific antibody levels was observed after the 23V dose in both groups. Heart transplant recipients had lower antibody responses compared with liver transplant recipients. Conclusions. Although the pneumococcal vaccine regimen was safe and immunogenic among pediatric solid organ transplant recipients, the patients did not seem to benefit from the second dose of PCV7 or from the 23V dose given 2 months later. Additional studies are needed to determine the number of PCV7 doses and the interval between PCV7 and 23V to induce optimal responses.