Protection against serotype 1 could not be demonstrated in two randomized trials of 9 valent pneumococcal conjugate vaccines. An analysis of the timing of type 1 cases among vaccinees and controls shows that the vaccine failures occurred among cases occurring after the first year of life. Vaccination was given as three doses in infancy with no booster dose. These data suggest that a booster dose given at 9 months of age, or early in the second year of life, should be evaluated for protection against type 1 pneumococcal disease.
