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Post-PCV7 changes in colonizing pneumococcal serotypes in 16 Massachusetts communities, 2001 and 2004.
- Author(s): Huang, Susan S;
- Platt, Richard;
- Rifas-Shiman, Sheryl L;
- Pelton, Stephen I;
- Goldmann, Donald;
- Finkelstein, Jonathan A
- et al.
Published Web Locationhttps://doi.org/10.1542/peds.2004-2338
ObjectiveThe introduction of heptavalent conjugate pneumococcal vaccine (PCV7) has raised concerns for replacement with nonvaccine serotypes in both invasive disease and asymptomatic carriage. Analysis of colonizing serotypes among healthy children in the community provides critical data on such changes.
MethodsNasopharyngeal specimens were obtained from children who were younger than 7 years during well-child or sick visits in primary care practices in 16 Massachusetts communities during 2001 and 2004. Susceptibility testing and serotyping were performed on isolated Streptococcus pneumoniae strains. Vaccination history with PCV7 was abstracted from the medical record.
ResultsAmong colonizing pneumococcal isolates, PCV7 serotypes decreased from 36% to 14%, and non-PCV7 serotypes increased from 34% to 55%. Overall carriage did not change (26% to 23%); neither did carriage of potentially cross-reactive serotypes (30% to 31%). The most common non-PCV7 serotypes were serotypes 11, 15, and 29. There was a substantial increase in penicillin nonsusceptibility from 8% to 25% in non-PCV7 serotypes; 35% were highly resistant to penicillin. Penicillin nonsusceptibility increased from 45% to 56% among PCV7 serotypes while remaining stable among PCV7 potentially cross-reactive strains (51% vs 54%).
ConclusionsPneumococcal colonization has changed after the introduction of PCV7, both in serotype distribution and in patterns of antibiotic resistance. The frequency of nonvaccine strains has increased, and the proportion of nonvaccine isolates that are not susceptible to penicillin has tripled. This shift toward increased carriage of nonvaccine serotypes warrants vigilance for changes in the epidemiology of invasive pneumococcal disease.
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