To evaluate the effectiveness of influenza vacation, we conducted analyses at both individual level and health region level. The association between influenza vaccination and hospital admission was examined among 128,677 subjects 12+ years of age who participated in a national survey in 2005. Both influenza and hospital admission proportions varied across health regions. Health regions with higher proportions of influenza vaccination had significantly lower proportions of hospitalization. A 10% increase in influenza vaccination less than 1 year ago was associated with a reduction of 11% in the risk of hospitalization over a 12-month time period at the health region level.
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