Pneumococcal resistance and serotype 19a in Pittsburgh-area children with acute otitis media before and after introduction of 7-valent Pneumococcal polysaccharide vaccine

Methods: Before and after introduction of pneumococcal conjugate vaccine (PCV7), the authors obtained nasopharyngeal (NP) specimens from 3 groups of children aged 6 to 23 months with acute otitis media (AOM): group 1 (pre-PCV7), group 2 (early post-PCV7), and group 3 (late post-PCV7). Results: Of the Streptococcus pneumoniae isolates, the proportion that were vaccine serotypes (VTs) declined progressively (60.4% vs 48.6% vs 5.2% in groups 1, 2, and 3, respectively; P 0.1 μg/mL; 26.7% vs 37.8% vs. 38.5%; P =.12); the proportion of isolates that were serotype 19A (4.0% vs 0% vs 25.9%; P <.001); and the proportion of 19A isolates that were penicillin-nonsusceptible (0% in group 1, 68.6% in group 3; P =.004). Conclusion: Shifts in pneumococcal serotype distribution and increases in penicillin nonsusceptibility among pneumococcal isolates from children with AOM underscore the need for continuing bacteriological surveillance for future vaccine development. © The Author(s) 2011