Polysaccharide-based pneumococcal vaccines in the prevention of acute otitis media.

New pneumococcal vaccines, consisting of 7-11 capsular polysaccharides coupled to protein carriers, are able to induce functionally active humoral and mucosal antibody responses. They also reduce mucosal carriage of pneumococci in the vaccinees. Preliminary results from efficacy trials suggest that about one-third of pneumococcal otitis could be prevented by using the seven-valent pneumococcal conjugate vaccine. If these efficacy estimates are true throughout childhood, up to 1.2 million episodes of acute otitis are preventable annually in the US. The true impact of the vaccine on otitis burden is dependent not only on the efficacy as demonstrated in the efficacy trials but also on the impact of the vaccine on the mucosal carriage of bacteria and on the herd immunity induced by vaccinations. Ongoing follow-up studies will reveal whether these factors increase or decrease the efficiency of the proposed vaccination programme.