Influenza- and respiratory syncytial virus-associated mortality and hospitalisations

The aim of the current study was to estimate influenza- and respiratory syncytial virus (RSV)-associated mortality and hospitalisations, especially the influenza-associated burden among low-risk individuals <= 65 yrs old, not yet recommended for influenza vaccination in many European countries. Retrospectively during 1997-2003, Dutch national all-cause mortality and hospital discharge figures and virus surveillance data were used to estimate annual average influenza- and RSV-associated excess mortality and hospitalisation using rate difference methods. Influenza virus active periods were significantly associated with excess mortality among 50-64-yr-olds and the elderly, but not in younger age categories. Influenza-associated hospitalisation was highest and about equal for 0-1-yr-olds and the elderly, and also significant for low-risk adults. Hospitalisation among children was mostly due to respiratory conditions, and among adults cardiovascular complications were frequent. RSV-active periods were associated with excess mortality and hospitalisation among the elderly. The highest RSV-related excess hospitalisation was found in 0-1-yr-olds. Influenza-associated mortality was demonstrated in 50-64-yr-olds. Among low-risk individuals <= 65 yrs of age, influenza-associated hospitalisation rates were highest for 0-4-yr-olds, but also significant for 5-64-yr-olds. These data may further support extension of recommendations for influenza vaccination to include younger low-risk persons. The respiratory syncytial virus-associated burden was highest for young children but also substantial for the elderly.