Summary. Studies were undertaken in adult groups aged 17-24 years, 25-64 years and 66-100 years to determine the haemagglutination-inhibiting antibody responses to sub-unit influenza vaccines containing A/USSR/90/77 (HlNl). Antibody responses to A/USSR/90/77 were low in all groups. The young adult group (17-24 years) produced a primary response to A/USSR/90/77 and showed a significant response to a second dose of vaccine, whereas their responses to the A/Texas/1/77 (H3N2) and B/Hong Kong/8/73 components were of the anamnestic type and showed no significant increase to a second dose. The adult (25-64 years) and aged (66-100 years) groups responded anamnestically to all three vaccine components. There was no impairment of the antibody response in the aged group in comparison with the response in the adult group. A comparative assay in microtitre trays and WHO plates showed two-to fourfold differences in antibody titre to A/USSR/90/77 in these systems.

Summary. Studies were undertaken with whole virus, subunit and adsorbed subunit influenza vaccines containing the A/New Jersey/8/76 strain to compare the antibody responses induced by immunization with these vaccines. There were no significant difl^erences in the haemagglutination-inhibition (HI) antibody responses to A/New Jersey/8/76 induced by these vaccines in the adult groups under study. Vaecinees over 23 years of age produced good HI antibody responses to one dose of vaecine. Neuraminidase antibody and complementfixing (CF) antibody responses were determined for the A/Victoria/3/75 component of bivalent vaccines. There were significant increases in neuraminidase inhibiting (NI) antibody titres but no increase in the complement-fixing antibody titres after vaccination.

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