Background: In Canada, a 7-valent pneumococcal conjugate vaccine (PCV-7) was licensed in 2001, and free vaccination of children <5 years of age was offered in December 2004 in the province of Quebec.
Objectives: To describe the frequency of physician claims for otitis media (OM) in relation to PCV-7 coverage during the period from 1996 to 2007.
Methods: The monthly frequency of OM claims in the population aged <10 years was obtained from the provincial health insurance board. Time series in different age categories were analyzed using structural models with unobserved components, including seasonality, linear trends, level changes, and outliers. The candidate explanatory variable was PCV-7 uptake rate as measured in the population <5 years of age in the Quebec City area.
Results: Free PCV-7 program implementation was followed by a marked increase in uptake and by the end of 2007, >90% of children had received >or=1 dose. In all models, seasonality was a major determinant of OM frequency rates and there were statistically significant downward trends, as well as downward level breaks and outliers. PCV-7 coverage (>or=1 dose) was a significant predictor in children 6 months to 2 years of age. The effect was of lesser magnitude and not significant in the group of children aged 2 to 4 years, and absent in the group 5 to 9 years. Since PCV-7 licensure, an estimated 100,000 visits were averted in children <5 years of age, and OM claim frequency reduction attributable to PCV-7 was 13.2% by the end of the study period.
Conclusion: PCV-7 implementation was associated with a significant reduction in the frequency of OM in the target population, and there was no indication of herd protection in older children.