PERSISTENCE OF ANTIBODIES TO PNEUMOCOCCAL CAPSULAR POLYSACCHARIDE VACCINE IN THE ELDERLY

Persistence of antibodies to 23-valent pneumococcal vaccine was assess ed among 62 subjects aged 65-88 years. IgG antibodies were measured by standardized EIA to serotypes 4, 6B, 9V, 14, 19F, and 23F before and 1 month, 1 year, and 3 years after vaccination. After satisfactory ant ibody responses (fold increases from 2.6 to 5.3), 3-year geometric mea n concentrations (GMCs) had waned to close (for types 4, 9V, and 23F) or similar (for types 6B and 19F) to their prevaccination values. Type 14 was exceptional: 1-month GMC was 7.7-fold and 3-year GMC was 3.0-f old in comparison to the prevaccination GMC. Antibody concentrations d ecreased at an equal rate irrespective of serotype and age or sex of t he vaccinee. The major factor predicting the persistence of antibodies above the prevaccination level was the magnitude of the original anti body response. Present results suggest that pneumococcal revaccination of the elderly may be needed as early as 3-4 years after the initial vaccination.