Immunogenicity of inactivated influenza vaccine in residential homes for elderly people.

One hundred and seventy residents of 11 Leicester City Council homes for the elderly, with a total of 515 beds, were studied during a 30-week period from September 1988 to March 1989 to determine the use of influenza vaccine, the levels of influenza antibody, the incidence of influenza, and the protection afforded by vaccination. The study group of 133 women and 37 men had a mean age of 85 years and 59% had one or more chronic medical conditions. The immunization rates by home for the 170 symptomatic residents ranged from 8% to 90% (mean 45%). Seventy-one sera, 36 from vaccinated and 35 from non-vaccinated residents were collected between 1 December 1988 and 24 March 1989 and were assayed for antibody to A/Taiwan/1/86 (H1N1), A Sichuan/2/87 (H3N2) and B/Beijing/1/87. Analysis revealed no statistically significant differences between the antibody profiles of vaccinated and unvaccinated subjects. Six influenza A and 6 influenza B infections were confirmed among the 170 subjects with upper respiratory tract infections. Influenza vaccination was not associated with significant levels of protection against influenza A or B. Studies of the haemagglutinins of the vaccine strains and influenza isolates during 1988/89 showed that they were closely related.