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.

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In a group of 32 adult volunteers given subunit influenza virus vaccine containing 250 international units (i.u.) of A/Victoria/3/75, 250 i.u. of A/Scotland/840/74 and 300 i.u. of B/Hong Kong/8/73, there were substantial increases in the geometric mean homologous haemagglutination-inhibiting (HI) antibody titres. There was also substantial boosting of the antibodies to the earlier variants of the Hong Kong (H3N2) series and to a later variant of the Asian (H2N2) series. There was no boosting of antibodies to the A/FM/1/47 strain, a representative member of the H1N1 series, but two individuals showed substantial rises to A/PR/8/34 (HON1). There were increases in the HI titre of antibodies cross reactive with two recent isolations, A/Texas/1/77, and A/Victoria/35/77, but the majority of vaccinees failed to reach antibody titres likely to be protective against such strains.

Feery, B. J., Matthews, R. N., Evered, M. G., and Gallichio, H. A. (1979). Aust. Paediatr. J., 15, 177–180. Antibody responses to influenza virus vaccine in children with acute lymphocytic leukaemia. Antibody responses to influenza immunization in children with acute lymphocytic leukaemia in remission were studied in two successive years. Initial antibody levels, the response to immunization, and final antibody levels were lower than in a group of children with cystic fibrosis. The results indicate that both primary and anamnestic antibody responses are depressed in children with acute leukaemia when they are on immunosuppressive therapy. Despite this depression the majority of the patients reached protective antibody levels to the A/Victoria/3/75 and A/Texas/1/77 (H3N2) antigens but not to the recent A/USSR/90/77 (H1N1) antigens.

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