Safety and Antibody Response, Including Antibody Persistence for 5 Years, after Primary Vaccination or Revaccination with Pneumococcal Polysaccharide Vaccine in Middle-Aged and Older Adults

Background. This study assessed antibody levels for 5 years after primary vaccination or revaccination with 23-valent pneumococcal polysaccharide vaccine (PN23). Methods. Subjects were enrolled into 4 study groups by age (50-64 or >= 65 years) and prior vaccination status (no prior vaccination or 1 vaccination 3-5 years previously). Blood was obtained on day 0 (before primary vaccination or revaccination), day 30, day 60, and annually during years 2-5. Levels of immunoglobulin G (IgG) to 8 vaccine serotypes were measured by enzyme-linked immunosorbent assay. Results. Of 1008 enrolled subjects, 551 completed year 5. For each serotype and age group, baseline geometric mean concentrations (GMCs) of IgG were higher in revaccination than primary vaccination subjects. Primary vaccination or revaccination with PN23 induced significant increases in levels of antibody to all serotypes tested. Although day 30 and 60 antibody levels tended to be modestly lower after revaccination, study groups had similar GMCs at later time points. For serotypes 4, 6B, 8, 9V, 12F, 14, and 23F, GMCs during years 2-5 after primary vaccination or revaccination remained higher than in vaccine-naive persons. Levels of antibody to serotype 3 returned to baseline by year 2. Conclusions. Both primary vaccination and revaccination with PN23 induce antibody responses that persist during 5 years of observation.