Relation of chronic disease and immune response to influenza vaccine in the elderly.

The ability of elderly patients to mount an adequate immune response to influenza vaccine has been debated. We studied the serum haemagglutination inhibition (HI) antibody response in elderly persons to determine whether different degrees of chronic illness were a critical factor in immune response. In autumn 1986, trivalent split virus vaccine was used to immunize 87 healthy ambulatory elderly adults and 53 institutionalized elderly adults. The pre-vaccination health status of the healthy elderly group was significantly better as measured by the incidence of chronic disorders and drug use (p less than 0.02) and by the Chronic Health Evaluation component of the APACHE severity of disease classification (p less than 0.001). No group differences were observed in serum HI antibody after immunization with the trivalent influenza vaccine. However, in 28 patients from each group who received the monovalent A/Taiwan/86(H1N1) vaccine 1 month after the trivalent vaccine, the percentage with a postvaccination HI titre greater than or equal to 40 was 57% (16 of 28) for the healthy elderly vs 7% (2 of 28) for the institutionalized elderly (p = less than 0.001). Geometric mean postvaccination HI titres were 31 and 13, respectively (p = 0.004). We concluded that the institutionalized elderly in our study mounted an inferior immune response against the new heterotypic influenza A/Taiwan strain when compared to healthy elderly adults. The Chronic Health Evaluation score may be an effective predictor of a poor immune response to new influenza vaccine strains in the elderly. Increasing age per se and lack of a history of prior influenza immunization did not adversely affect the development of protective levels of serum antibody.(ABSTRACT TRUNCATED AT 250 WORDS)