Response to influenza vaccination in community and in nursing home residing elderly: relation to clinical factors.

Intramuscular (IM) influenza vaccines are about 50% effective in preventing respiratory illness among the elderly. The aim of this study was to identify factors associated with immune response to influenza vaccination among nursing home and community-residing elderly. 114 nursing home (NHE) and 62 community residing elderly (CE) were vaccinated with a commercial IM vaccine. Serum antibodies were evaluated by HIA, and the impact of subjects' clinical characteristics on seroconversion was determined. Factors that were associated with low seroconversion among NHE, included: type II diabetes [for B/Harbin: p=0.044, OR 0.12, (CI: 0.015-0.94)], and antibody titer prior to vaccination A/(H1N1): p=0.03, OR 2.38, (CI: 1.09-5.22); A/(H3N2): p=0.015, OR 2.68 (CI: 1.22-5.92), B/Harbin: p=0.057, OR 4.46 (CI: 0.96-20.85)]. Factors that were associated with lower seroconversion CE elderly, included older age [A/(H1N1): p=0.008, OR 0.846, (CI 0.75-0.96), B/Harbin: p=0.016, OR 0.812, (CI:0.69-0.96)], and antibody titer prior to vaccination A/(H1N1): p=0.029, OR 4.08, (CI: 1.16-14.37); A/(H3N2): p<0.0001, OR 11.495 (CI: 3.18-41.55)]. There was no significant difference in seroconversion between nursing home residing elderly and community elderly. We conclude that Type-II diabetes and antibody titer>1:40 prior to vaccination are associated with reduced response to the influenza vaccination in nursing home elderly.