Epidemiological studies of Streptococcus pneumoniae in infants: antibody to types 3, 6, 14, and 23 in the first two years of life.

Antibodies to pneumococcal types 3, 6, 14, and 23 were measured in sera from 78 infants prospectively studied from birth. Mean levels of antibodies to capsular antigens were 2-4 micrograms/mL, with no overall differences between carriers and noncarriers of given types. Serial serum samples were studied in selected infants to more precisely define the antibody response in relation to specific pneumococcal colonization and infection. Although some infants had little antibody, and made little in response to exposure, others had demonstrable antibody at the onset of acute otitis media. The highest levels were seen following repeated exposure. After an initial or secondary response, levels declined with or without continued nasopharyngeal carriage.