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Prior to the advent of the 7-valent pneumococcal conjugate vaccine (PCV7) in 2000, more than 16,000 U.S. children younger than 5 years acquired pneumococcal infections annually. Investigators analyzed U.S. surveillance data from 2001–2004 to identify the incidence and serotypes of invasive pneumococcal infections in children aged <5 years who received one or more doses of PCV7.
Of 753 invasive pneumococcal infections identified, 155 (21%; median patient age, 13 months) were caused by serotypes covered by the vaccine. The proportion of such cases decreased significantly with increasing number of vaccine doses; 45% of breakthrough infections occurred in children who had received only one dose. Twenty-seven cases (4%; median age, 27 months) wer…