Otitis media is a common pediatric disease and the main reason for antibiotic prescription in children. Before implementation of routine childhood pneumococcal vaccination in Germany, serotypes contained in the seven-valent pneumococcal conjugate vaccine (PCV) were among the most frequent pneumococcal serotypes responsible for acute otitis media (AOM). This report describes the first 3 years of a prospective, multicenter, epidemiological cross-sectional study examining the bacteriology of middle ear fluids (MEF) and nasopharyngeal swabs (NPS) of children 2 months to 5 years of age with spontaneously perforated AOM in the era of routine pneumococcal vaccination. MEF was obtained from 963 subjects; NPS from 877. Reported case numbers steeply decreased over the three study years even though the recruiting base remained the same. Among subjects with relevant bacterial growth in their MEF swabs, 113 (11.7%) had Streptococcus pyogenes, 97 (10.1%) Staphylococcus aureus, 88 (9.1%) Streptococcus pneumoniae, 63 (6.5%) Haemophilus influenzae, and 8 (0.8%) Moraxella catarrhalis. S. pneumoniae isolates decreased from 41 (9.3%) in year 1 to 12 (5.7%) in year 3 (p = 0.128). PCV7 serotypes accounted for only 7.9% (n = 7) of isolated pneumococci. Of the 877 subjects with NPS cultures, 465 (53.0%) carried S. pneumoniae, 314 (35.8%) H. influenzae, 292 (33.3%) M. catarrhalis, and 110 (12.5%) S. pyogenes; 79.4% (n = 765) of the children were vaccinated with at least one dose of PCV. Carriage of pneumococci was slightly lower in vaccinated (47.8%) than in unvaccinated (52.7%) children (p = 0.254). PCV7 serotypes were carried by 9.6% of unvaccinated children but by only 4.2% of vaccinated children, resulting in a 56.3% vaccine effectiveness.
Conclusions: Following universal PCV7 immunization, a clear epidemiological impact of pneumococcal conjugate vaccination was observed as PCV7 serotypes have almost disappeared among AOM.