The unmet need in the elderly: designing new influenza vaccines for older adults.

Influenza is a serious illness and probably the single most important cause of excess disability and mortality during the winter months. In spite of limited efficacy in older adults, influenza vaccination is nevertheless a cost-saving medical intervention since it does reduce hospitalisation and death rates due to pneumonia, exacerbations of heart failure and, surprisingly, heart attacks and strokes. Yet hospitalisation and death rates for acute respiratory illnesses continue to rise in spite of widespread vaccination programs. As a person ages, the immune response to antigenic stimulation with the influenza virus shifts toward T helper type 2 cytokine production. This is associated with a relative reduction in cytotoxic T-cell activity and a reduced capacity to destroy infected host cells and clear the virus from infected lung tissue. Breakthrough strategies to improve the current influenza vaccines are required to avoid a crisis in health care. A targeted approach will develop vaccines that can reverse these age-related changes in T-cell responses, particularly the functions of cytotoxic T lymphocytes.