Seasonal and pandemic influenza vaccines for the elderly and other risk groups: a review of available data.

Human seasonal influenza is a large burden of morbidity and mortality for societies, affecting mainly elderly people and those with underlying chronic medical conditions. Annual vaccination of older adults and other risk groups is the most effective measure for reducing morbidity and mortality associated with infection. A 2008 survey showed 40-fold differences between the vaccination coverage in various European Union countries in individuals aged >or=65 years, ranging from less that 2% to more than 80% in the 2006-2007 season, with Poland belonging to the countries with low influenza vaccination coverage. Annual monitoring of the vaccination coverage is crucial for achieving and maintaining high uptake levels. The need to pay for the vaccine out of pocket is a strong factor discouraging vaccination, and there is evidence that reimbursing costs of influenza vaccination influences vaccination coverage. Although annual influenza immunization of healthcare workers is an important method of preventing the nosocomial transmission of influenza and decreasing the exposure of vulnerable patients, worldwide influenza vaccination rates among healthcare personnel are unacceptably low, rarely exceeding 40%. It is important to keep high vaccination coverage among elderly nursing-home residents. More research is needed to clearly establish the effect of dose sparing strategies of influenza vaccination, e.g., via intradermal immunization, on the immune response in elderly recipients. Finally, due to the emergence of the pandemic influenza A (H1N1) 2009 virus and the development of vaccines directed towards it, the upcoming influenza season 2009-2010 will pose a particular challenge to influenza vaccination programs, and will require careful planning.