Reduction in hospitalizations for pneumonia associated with the introduction of a pneumococcal conjugate vaccination schedule without a booster dose in Australia

Background: Postmarketing surveillance of heptavalent pneumococcal conjugate vaccine (7vPCV) has shown significant reductions in admissions coded as pneumonia in countries where a booster dose is given in the second year of life. In Australia, a 3-dose primary schedule at 2, 4, and 6 months of age without a booster has been funded nationally for non-Indigenous children since 2005. Methods: All hospital discharges in Australia with the primary diagnosis coded as pneumonia between July 1998 and June 2007 were identified from a national electronic database. Monthly rates of hospitalization for pneumonia over this period were determined for the age groups <2, 2-4, 5-17, 18-39, 40-64, and 65 years. Negative binomial regression modeling, adjusting for background and seasonal trends, was used to quantify the effect of the 7vPCV program. Results: A total of 523,591 eligible hospital discharges were identified. In the 30 months following 7vPCV introduction, there were significant adjusted reductions in all-cause pneumonia in children aged <2 and 2 to 4 years of 38% (95% CI = 36%-40%), and 29% (26%-31%), respectively. Reductions of between 3% and 11% were observed in the older age groups. Interpretation: The significant differential effects observed are strongly suggestive of the PCV7 program being responsible for the observed reduction in pneumonia hospitalizations in Australia, and the magnitude was comparable to that documented in countries with a booster dose. This finding appears robust and may be related to high levels of vaccination coverage and catch-up early in the program, or to relatively lower levels of serotype replacement without a booster dose.