Local and systemic immune response in community-dwelling elderly after intranasal or intramuscular immunization with inactivated influenza vaccine

Intramuscular (IM) influenza vaccines are about 50% effective in preventing clinical illness among the elderly and their effectiveness in eliciting mu cosal response may be even lower. The aim of the present study was to evalu ate the immunological effect of a novel inactivated intranasal (IN) trivale nt whole influenza virus vaccine among community-dwelling elderly. Sixty-on e subjects were vaccinated with two doses of an IN vaccine and a control gr oup of 31 subjects was vaccinated with a commercial IM vaccine. Viral strai ns in the 1997/8 vaccine used were A/Nanchang/933/95(H3N2), A/Johannesburg/ 82/ 96(H1N1) and B/Harbin/7/94. Serum IgG and nasal IgA were determined by HI and ELISA, respectively. Only a few minor local adverse events were repo rted after vaccination. Seroconversion for the three antigens tested was hi gher after IM vaccination, although not statistically significant. Local an tibody response to the three antigens tested was detected in 50-53% and 19- 26% of IN and IM immunized subjects, respectively. The IN vaccine tested wa s significantly more effective than the IM vaccine in inducing mucosal IgA response. This may prevent influenza at its early stages and thus contribut e to the reduction of complications in the elderly. J. Med. Virol. 67:700-7 06, 2000. (C) 2000 Wiley-Liss, Inc.