Efficacy of pneumococcal polysaccharide vaccine in preventing acute otitis media in infants in Huntsville, Alabama.

In a study of the efficacy of pneumococcal capsular polysaccharide vaccines in preventing otitis media due to Streptococcus pneumoniae, 179 infants were randomly assigned to receive either a "target" vaccine containing serotypes 1, 3, 6, 7, 14, 18, 19, and 23 (which account for most cases of pneumococcal otitis media) or a control vaccine containing serotypes 2, 4, 5, 8, 9, 12, and 25 (which account for few cases). Vaccine (0.5 ml) was administered subcutaneously; a dose contained 25 micrograms of each serotype. The incidence of otitis media due to "target" serotypes was determined in both groups. There were not significant differences between vaccines and controls in either the incidence or etiology of episodes of otitis media before immunization. During a two-year follow-up, no significant difference was observed regarding the incidence of episodes due to "target" serotypes in infants who were immunized after 12 months of age. However, of 66 control infants immunized before 12 months of age, 22 experienced 33 pneumococcal episodes due to a "target" serotype, whereas only 13 of 67 vaccines accounted for 22 such episodes. Among infants who had two or fewer episodes before immunization, four vaccines and 13 controls continued to have episodes of otitis media and became "otitis prone," i.e., six or more episodes (chi 2 = 4.84; P = 0.05). Low levels of serum antibody were not protective, and in one case a level of 609 ng of antibody nitrogen/ml of middle ear effusion was not protective. Thus, although the vaccine may be associated with a lower incidence of otitis media, the results of this study do not show a statistically significant efficacy of the vaccine.