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Background: Based on two clinical trials in healthy infants the American Academy of Pediatrics (AAP) advices immunization with a 7-valent pneumococcal conjugate vaccine in children with recurrent acute otitis media (AOM)., Objective: To study the efficacy of a 7-valent pneumococcal conjugate vaccine on acute otitis media recurrences, its immunogenicity and impact on nasopharyngeal Streptococcus pneumoniae carriage in children with a history of frequent acute otitis media., Methods: In this double-blind, randomized study, 74 Belgian children, aged 1-7 years, with at least 2 clinically diagnosed episodes of acute otitis media in the previous year were enrolled. Children were immunized with either a 7-valent pneumococcal conjugate vaccine followed by a 23-valent pneumococcal polysaccharide booster or a control hepatitis A vaccine. Total follow-up was 26 months., Results: Despite adequate serum IgG responses to all conjugate vaccine pneumococcal serotypes, no reduction of acute otitis media episodes was observed in the pneumococcal vaccine group as compared to the control group (rate ratio: 1.16; 95% CI: 0.69-1.96). Overall nasopharyngeal pneumococcal carriage remained stable. However, a transient shift from conjugate vaccine related S. pneumoniae serogroups to non-vaccine related serogroups was noted following conjugate vaccination., Conclusion: Clinically no protective effect of pneumococcal conjugate vaccination on acute otitis media recurrences was found in children with a history of frequent AOM.

Objective: To evaluate the isotype and IgG subclass distribution of anti-pneumococcal antibodies and response to polysaccharide vaccination in otitis prone children., Methods: IgG1, IgG2 and IgA antibodies to pneumococcal serotypes 3, 4, 6B, 9V, 14, 19F and 23F were determined in otitis prone children and in an age-matched healthy control population. Patients were immunized with a 23-valent pneumococcal polysaccharide vaccine. The antibody response was measured 4 weeks later., Results: Geometric mean IgA and IgG2 antibody levels for all seven pneumococcal serotypes tested were significantly lower in otitis prone children than in the control population. After immunization, there was no significant increase in geometric mean IgG2 anti-serotype 6B, 19F and 23F pneumococcal polysaccharide (weak immunogenic), but also no increase for IgG2 anti-serotype 4 and 14. Post immunization IgG2 antibody titers for serotypes 6B, 9V and 19F even remained below titers of non-vaccinated controls. Nine out of 29 otitis prone children were colonized nasopharyngeally with Streptococcus pneumoniae during the time of vaccination; these children had an even more severely impaired systemic antibody response., Conclusions: Otitis prone children, while having normal IgG1 antibody levels, have low IgG2 and IgA anti-polysaccharide antibody levels and fail to respond in these subclasses upon vaccination with pneumococcal polysaccharide vaccine.