Immunogenicity and safety of 13-valent pneumococcal conjugate vaccine in children previously immunized with 7-valent pneumococcal conjugate Vaccine

Background: The 7-valent pneumococcal conjugate vaccine (PCV7) has proven highly effective in preventing diseases caused by Streptococcus pneumoniae; however, in some regions, serotype coverage is limited. A recently licensed 13-valent PCV (PCV13) was developed to provide additional coverage globally. Children previously vaccinated with PCV7 could benefit from supplemental vaccination with PCV13 to provide protection against the 6 additional serotypes in PCV13. This open-label study evaluated the immunogenicity and safety of administering PCV13 to healthy children previously vaccinated with PCV7. Methods: Children between 15 months and 2 years of age (group 1) received 2 doses of PCV13; children between 2 and 5 years (group 2) received 1 dose. Antibodies (immunoglobulin G) against the polysaccharide antigens in PCV13 were measured before vaccination and 1 month after the final dose. Solicited local and systemic adverse events (AEs) were collected for 7 days postvaccination. Unsolicited and serious AEs were collected throughout. Results: A total of 284 subjects (group 1: n = 109; group 2: n = 175) had blood available for testing. Antipneumococcal immunoglobulin G geometric mean fold rises ranged from 2-to 19-fold for the PCV7 serotypes and from approximately 2-to 124-fold for the 6 additional serotypes. Additionally, postvaccination titers in excess of 0.35 μg/mL, the serologic correlate of immunity against pneumococcus for children, occurred in 98% of subjects in both groups for 12 of the 13 serotypes in PCV13. Slightly lower percentage of subjects, 94.5% and 92% of subjects in group 1 and group 2, respectively, had postvaccine titers for serotype 3 exceeding the serologic correlate of immunity. Reactogenicity was typically mild and self-limited, and unsolicited AEs reported were generally consistent with common childhood illnesses. Conclusion: PCV13 was safe and immunogenic when administered to children who had previously received PCV7, and can be used for supplemental vaccination to provide additional protection against the 6 additional serotypes. © 2011 by Lippincott Williams & Wilkins.