For reasons that are not yet clear, memory T cells from aged individuals do not react as quickly or for as great a duration as cells from younger subjects. Numerous studies have examined means of improving the efficacy of vaccines for the aged. Novel types of vaccine delivery using, for example, liposomes or naked DNA to create a more powerful immune response, are being developed. Alternative adjuvants such as IL-2 are being tested to boost vaccine efficacy. New methods of vaccination, like using nasal sprays or oral vaccines to stimulate mucosal immunity , instead of the traditional injections, are also being explored.
Nutrition plays a prominent role in immune response, and the elderly often suffer from malnutrition.
Reduced caloric intake is known to slow the aging process and help maintain higher numbers of naive T cells and levels of IL-2. Vitamin E and zinc in particular are important nutrients for the proper functioning of the immune system. Long-term zinc deficiency in the elderly causes a decrease in cytokine production and impaired regulation of helper T cell activity. In both mice and humans, a daily dose of vitamin E significantly higher than the U.S. Recommended Daily Allowance improved T cell function in cell-mediated immunity. Vitamin E is also an antioxidant that can protect lymphocytes, the brain, and other tissues from destructive free radicals.