Different protection rates in various groups of volunteers given subunit influenza virus vaccine in 1976

Different rates of protection were observed in various groups of volunteers given trivalent subunit influenza virus vaccine during an epidemic caused by A/Victoria/3/75 strains of influenza virus in Melbourne, Victoria, Australia, in 1976. The degree of protection varied from 80% protection from infection in one group to a moderation in the severity of clinical illness in a geriatric group. The response to immunization may depend on the previous experience of the vaccinees, and it may be necessary to use different dose schedules in different groups for optimal protection.