| efficacy of influenza vaccine in elderly persons in welfare nursing homes: reduction in risks of mortality and morbidity during an influenza a (h3n2) epidemic. | the effect of influenza vaccination on the occurrence and severity of influenza virus infection in a population residing in nursing homes was studied through a program by the osaka prefectural government, which is the first and official support for influenza vaccination of the elderly population during an influenza a (h3n2) epidemic in japan: | 2001 | 11382801 |