The intradermal vaccination route – an attractive opportunity for influenza vaccination in the elderly

An age-related decline in functioning of the innate and adaptive immune systems results in increased susceptibility to infections (e.g. influenza) and decreased responses to vaccination in elderly people. A satellite symposium held during the xixth IAGG World Congress of Gerontology and Aging in Paris, 5–9 July 2009, considered the potential of intradermal vaccination to enhance immune responses in the elderly. The rich supply of capillary blood and lymphatic vessels in the dermis, along with its resident population of dendritic cells, make the skin an attractive site for vaccine delivery. Intanza® 15 μg is a purified, inactivated, trivalent, split-virus influenza vaccine containing 15 μg haemagglutinin/strain/0.1 ml dose that is administered using a novel intradermal microneedle injection system. A randomised, open-label phase III trial in 3695 people aged 60–95 years found that antibody responses to the intradermal influenza vaccine were superior to those for the same vaccine administered intramuscularly. The systemic safety profile of the intradermal vaccine was comparable with that of the intramuscular vaccine, but rates of injection-site reactions were higher with the intradermal vaccine, reflecting the close proximity of injected vaccine to the skin surface. The increased immunogenicity of Intanza® 15 μg in the elderly compared with the standard intramuscular influenza vaccine supports the concept of intradermal vaccination to enhance immune responses in elderly people.