Antibody Response to 1995–1996 Influenza Vaccine in Institutionalized and Non-Institutionalized Elderly Women

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Abstract
Background: Concern about poor responsiveness to influenza vaccination by institutionalized elderly people. Objective: To determine whether institutionalized elderly volunteers develop a significant antibody response following influenza vaccine and to compare this response with that of non-institutionalized subjects. Methods: The haemagglutination-inhibiting antibody response after 1995–1996 influenza vaccination [A/Shangdong/9/93 (H3N2), A/Taiwan/1/86 (H1N1), B/Panama/45/90] was estimated in 80 elderly women living in a nursing home and compared with that of 51 non-institutionalized women. Results: No differences were found in the prevaccination status, and, after vaccination, a significant humoral response was elicited both in institutionalized and non-institutionalized elderly subjects against all three influenza strains tested. The immune response of institutionalized patients was satisfactory and significantly higher than that observed in non-institutionalized women. These results were confirmed both by a separate analysis of homogeneous subgroups stratified according to the presence in the two cohorts of potential causes of differential antibody response (prevaccination antibody titre, age, long-term drug treatment, risk factors for influenza infection, and physical disability) and by logistic regression analysis in order to adjust immune responses for the different variables. Conclusion: Influenza vaccination is effective in elderly people living in nursing homes. However, the postvaccination antibody response to influenza vaccine is influenced by different factors directly or indirectly related to residence.