First and second dose antibody responses to pneumococcal polysaccharide vaccine in infants.

Total (radioimmunoassay) and immunoglobulin class-specific (enzyme-linked immunosorbent assay) antibody responses to pneumococcal capsular polysaccharides were measured in children who received the first dose of 14-valent pneumococcal or control (saline) vaccine at the age of 7 months and the second dose at the age of 13 months. Types 3 and 18C elicited strong antibody responses and types 14 and 19F elicited intermediate responses in all immunoglobulin classes after both doses of the vaccine. The generally poor immunogen types 6A and 23F elicited a weak antibody response mainly in the immunoglobulin M class. The antibody levels to most pneumococcal types also decreased rapidly after both injections of the vaccine.