Clinical studies of pneumococcal vaccines in infants. II. Efficacy and effect on nasopharyngeal carriage.

Two polyvalent pneumococcal polysaccharide vaccines were evaluated in about 200 infants. Vaccination did not affect nasopharyngeal carriage of pneumococci nor was titer of type-specific antibody, as determined by radioimmunoassay, predictive of subsequent carriage of individual types. Otitis media occurred with equal frequency in vaccinated and in control children. One of four episodes of documented pneumococcal bacteremia occurred after vaccination and was caused by a type contained in the vaccine. No indication of either an efficacious or detrimental effect of pneumococcal polysaccharide vaccines administered to infants was seen in this study.