The impact of heptavalent pneumococcal conjugate vaccine (PCV7) on transmission of antimicrobial-resistant Streptococcus pneumoniae is an important concern for countries considering PCV7 introduction.Methods:
Every winter from 2000 to 2004, as PCV7 was routinely introduced, we obtained nasopharyngeal swabs for pneumococcal culture, serotyping, and susceptibility testing from 150 children aged 3–59 months at each of 3 Anchorage, Alaska clinics. We assessed risk factors for pneumococcal carriage, including vaccination status and antimicrobial use.Results:
Between 2000 and 2004, 2250 nasopharyngeal swabs from 2061 infants and children were collected. The proportion of children receiving ≥1 PCV7 vaccination increased from 0 to 89%, whereas overall pneumococcal carriage remained stable (38% versus 41%, respectively). Among S. pneumoniae carriers, we observed declines in carriage of PCV7 serotypes (from 54% to 10%, P < 0.01) and trimethoprim-sulfamethoxazole nonsusceptible strains (44% to 16%, P < 0.01), but not in PCN-nonsusceptible strains (36% versus 37%). Among PCN-nonsusceptible types, the proportion of serotype 19A strains increased from 10% to 32% (P = 0.0002). Recent β-lactam use was stable throughout the period (29% overall), whereas trimethoprim-sulfamethoxazole use declined from 6% to 2% (P = 0.02).Conclusions:
PCV7 vaccination in the first 5 years did not affect overall pneumococcal carriage, but was associated with a shift in serotype distribution from PCV7 types to non-PCV7 types. With persistent pressure of some antimicrobials, reductions in carriage of antimicrobial nonsusceptible PCV7 types may be offset by increases in carriage of nonsusceptible non-PCV7 types.