Abstract
We tested whether the effect of influenza activity on invasive pneumococcal disease incidence and severity varies between age and co-morbidity groups.
Weekly rates of invasive pneumococcal disease were obtained from the Danish National Laboratory Surveillance System (1977–2007). Influenza-like illness data were collected from a-sentinel surveillance system, Statens Serum Institut. We fit Poisson regression models for invasive pneumococcal disease, with predictors for seasonality, trends, and influenza activity, and allowed the influenza activity variable to vary by co-morbidity level and clinical presentation.
Influenza activity accounted for 8.4% (95%CI 4.8−11.9%) and 6.9% (95%CI: 5.4–10.2%) of all invasive pneumococcal disease cases among 15–39 and 40+ year olds, respectively but had no measureable impact among children under 15 years. Influenza activity was associated with significant increases in the incidence of invasive pneumococcal pneumonia in both children and adults. The association was more pronounced among younger adults without co-morbidities. Case-fatality also varied seasonally among the elderly, and this variation might be associated with influenza activity.
Pneumococcal incidence and the severity of disease varied seasonally and between age groups. The effect of influenza activity on pneumococcal disease varied between children and adults, and this difference was largely due to differences in disease presentation.
- ERS