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The introduction of the heptavalent pneumococcal conjugate vaccine (PCV7) in the U.S. in 2000 was a welcome addition to our preventive armamentarium; however, questions remain regarding the degree of protection in immunized children with fever or pneumonia. Two studies examined recent trends in invasive pneumococcal infection.
In the first study, researchers used data from the Nationwide Inpatient Sample to evaluate discharge diagnoses in more than 35 million hospital admissions before (1997–1999) and after (2001–2004) routine immunization with PCV7 in the U.S. Among children younger than 2 years, admissions for pneumonia decreased by 39% overall and by 65% for pneumonia attributed to Streptococcus pneumoniae.
In the second study, investigators analyzed serotypes of colonization and invasive pneumococcal disease (IPD) from 1995 through 2006 in highly immunized children younger than 2 years in Alaska. During the first years after introduction of routine PCV7 (2001–2003), Native Alaska children had a dramatic (67%) decrease in IPD, but the decrease was followed by an 82% increase from 2003 through 2006. The increase was due to non-PCV7 serotypes, most commonly 19A. Non–Native Alaska children had a sustained decrease in IPD.
Grijalva CG et al. Decline in pneumonia admissions after routine childhood immunisation with pneumococcal conjugate vaccine in the USA: A time-series analysis. Lancet 2007 Apr 7; 369:1179-86.
Singleton RJ et al. Invasive pneumococcal disease caused by nonvaccine serotypes among Alaska Native children with high levels of 7-valent pneumococcal conjugate vaccine coverage. JAMA 2007 Apr 25; 297:1784-92.
Comment
Although PCV7 clearly has had an effect on invasive pneumococcal infections in the pediatric population, pockets of at-risk children exist, such as the Native Alaska children in this study and, as previously reported, some children in Salt Lake City. In addition, anecdotal reports have been circulating about an increased incidence of infections with non-vaccine S. pneumoniae strains 1, 3, and 19A in other parts of the country. We must continue to be vigilant in the evaluation of all febrile children and children with pneumonia, regardless of immunization status. When invasive pneumococcal disease is identified, isolates should be typed and sent to public health laboratories so we may better understand the evolving epidemiology.