Invasive Pneumococcal Disease Among Infants Before and After Introduction of Pneumococcal Conjugate Vaccine

Results There were 146 cases of IPD, 89 before and 57 after PCV7 introduction. Isolated bacteremia occurred in 94 cases (64%), pneumonia in 27 (18%), meningitis in 22 (15%), and septic arthritis and/or osteomyelitis in 3 (2%). Mean rates of IPD for infants aged 0 to 90 days decreased 40% from 11.8 (95% confidence interval (CI), 9.6-14.5) to 7.2 (95% CI, 5.6-9.4; P=.004) per 100000 live births following PCV7 introduction. Among black infants, mean rates of IPD decreased significantly from 17.1 (95% CI, 11.9-24.6) to 5.3 (95% CI, 2.8-10.1; P=.001) per 100000 live births, with a nonsignificant decrease from 9.6 (95% CI, 7.3-12.7) to 6.8 (95% CI, 4.9-9.4) per 100000 live births for white infants. Rates of PCV7-serotype isolates decreased sig- nificantly from 7.3 (95% CI, 5.3-10.1) to 2.4 (95% CI, 1.6-3.8; P.001) per 100000 live births, while rates of non-PCV7 serotypes remained stable (P=.55). Conclusions Since PCV7 introduction, rates of IPD in young infants have de- creased significantly, providing evidence that vaccinating children aged 2 to 23 months has led to changes in pneumococcal carriage in infants too young to receive PCV7. With a significant decrease in rates of IPD among black infants, the previous racial difference has been eliminated.