Influenza vaccination in high-risk groups: a revision of existing guidelines and rationale for an evidence-based preventive strategy.

Influenza, an infectious respiratory disease, is one of the main causes of excess winter deaths (EWDs) in Europe. Annual flu epidemics are associated with high morbidity and mortality rates, especially among the elderly, those with underlying health conditions and pregnant women. Health Care Workers (HCWs) are also considered at high risk of both contracting influenza and spreading the virus to vulnerable patients. During the 2014/2015 season, the excess winter mortality rates observed in countries of the northern hemisphere (EuroMOMO network) and in Italy (+13%) were strongly related to the intensity of influenza circulation. Influenza vaccination is the most important public health intervention to prevent seasonal influenza transmission and infection. However, to date, influenza vaccination coverage reported in Europe (including high-risk groups) is still largely unsatisfactory. This study analyzes some international and European guidelines on influenza vaccination and the rationale that underlies evidence- based public health intervention for the prevention of influenza among the principal high-risk groups: a) the elderly (subjects aged 65 years or older); b) subjects with underlying health conditions; c) pregnant women; d) healthcare workers. Only by achievement recommended influenza vaccination coverage among high-risk groups in all European countries can we reduce the burden of disease.