Adjuvanted vaccines against influenza in the elderly

Influenza is an important public health issue, especially with the aging of the population, since the most serious consequences of the illness affect the elderly. Between 1979 and 2001, approximately 41000 annual deaths have been attributed to influenza in the United States (Dushoff, 2005). Annual vaccination is a key strategy employed to combat this illness, and while it is very effective in healthy young adults, it is much less successful in the elderly. The impaired immune system with aging may contribute to this diminished ability of the vaccine to afford protection. Strategies to improve vaccine efficacy, particularly for the aged population, are necessary. One potential strategy is the inclusion of adjuvants in the vaccine formulations to enhance the immune response. Adjuvants have been shown to improve antibody production, allow dose-sparing, and potentially increase cross-reactivity. These benefits are important in combating both seasonal influenza and pandemic influenza, as current seasonal vaccine effectiveness depends on close matching to the circulating virus, and fast production of pandemic vaccines are key to their effectiveness. While much is still unknown about adjuvants, especially their mechanisms of action, their potential at improving the efficacy of influenza vaccines has been well recognized, particularly in the elderly.