The CAPITA study of protein-conjugate pneumococcal vaccine and its implications for use in adults in developed countries.

Until 1990, Hemophilus influenzae type b (HITB) was a major cause of morbidity and mortality in toddlers and young children. A vaccine consisting of purified polyribosyl ribitol phosphate (PRP), the capsular polysaccharide (CPS) of HITB, had been shown to be ineffective as an antigen in the population at risk, and this vaccine was withdrawn from the market within a few years of its introduction. By contrast, the discovery that PRP, when covalently bound to an antigenic protein, stimulated antibody production in infants and toddlers, (1) led to the development of a vaccine that has all but eradicated HITB infection and brought about a near-disappearance of this organism in the United States.