Antibody response to influenza vaccination in the elderly: a quantitative review.

We performed a quantitative review of 31 vaccine antibody response studies conducted from 1986 to 2002 and compared antibody responses to influenza vaccine in groups of elderly versus younger adults. We did a weighted analysis of the probability of vaccine response (measured as seroconversion and seroprotection) for each vaccine component (H1, H3 and B antigens). Using a multiple regression model, we adjusted for factors that might affect the vaccine response. The adjusted odds-ratio (OR) of responses in elderly versus young adults ranged from 0.24 to 0.59 in terms of seroconversion and seroprotection to all three antigens. The CDC estimates of 70-90% clinical vaccine efficacy in young adults and these estimates suggest a corresponding clinical efficacy in the elderly of 17-53% depending on circulating viruses. We conclude that the antibody response in the elderly is considerably lower than in younger adults. This highlights the need for more immunogenic vaccine formulations for the elderly.