Influenza-related mortality in the Italian elderly: no decline associated with increasing vaccination coverage

Abstract

We investigated trends in influenza-related mortality among the elderly population in Italy associated with increased vaccination coverage. Using Italian vital statistics data, we studied monthly death rates for pneumonia and influenza and all-cause for persons >/=65 years of age by 5-year age groups for 1970-2001. Using a classic seasonal regression modelling approach, we estimated the age-specific seasonal excess mortality rates among Italian elderly as a measure of influenza-related deaths. We studied trends in excess mortality after adjusting for population aging and analyzing separately seasons dominated by the severe A/H3N2 subtype and those dominated by other circulating influenza subtypes. After the late 1980s, no decline in age-adjusted excess mortality was associated with increasing influenza vaccination distribution primarily targeted for the elderly. These findings suggest that either the vaccine failed to protect the elderly against mortality (possibly due to immune senescence), and/or the vaccination efforts did not adequately target the frailest elderly. As in the US, our study challenges current strategies to best protect the elderly against mortality, warranting the need for better controlled trials with alternative vaccination strategies.