Efficacy of influenza vaccine in the elderly: reduction in risks of mortality and morbidity during an influenza A (H3N2) epidemic for the elderly in nursing homes.

The effect of influenza vaccination on the occurrence and severity of influenza virus infection in elderly nursing home residents was studied during an influenza A (H3N2) epidemic in Japan. Of 22,462 individuals living in 301 welfare nursing homes, 10,739 received inactivated (subunit) influenza vaccine. Through the period November 1998 to March 1999, there were 950 cases of influenza infection diagnosed clinically, with virus isolation and/or serology. There were statistically significantly fewer cases of influenza, hospital admissions due to severe infection, and deaths due to influenza in the vaccinated cohort compared with the unvaccinated controls. No serious adverse reactions to vaccination were recorded. Thus influenza vaccination is safe and effective in this population, and should be an integral part of the routine care of persons aged 65 years and over residing in nursing homes.