Dose-Response Relationship after Immunization of Volunteers with a New, Surface-Antigen-Adsorbed Influenza Virus Vaccine

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Abstract
Volunteers (15 per group) were given inoculations of various .doses (5–400 international units [IU]) of surface-antigen-adsorbed influenza virus A/Port Chalmers/ 73 vaccine; this vaccine was prepared from purified virus hemagglutinin and neuraminidase antigens and adsorbed to alhydrogel. The titers of hemagglutinationinhibiting (HAl) and neuraminidase-inhibiting antibodies in serum after immunization showed a clear dose-response relationship. Thus, for volunteers given 400, 100, 25, or 5.0 IV of vaccine, the titers of HAl antibody in serum increased 174−, 32−, 12−, and eightfold, respectively. A similar dose response was observed for production of local neutralizing antibody. Immunization with A/Port Chalmers/73 virus vaccine also induced serum HAl antibody to influenza viruses A/Scotland/74, A/England/ 72, and A/Hong Kong/68; the increase in titers of antibody to these viruses corresponded directly to the degree of cross-reactivity between the virus tested and the vaccine virus. Four weeks after immunization, all volunteers were challenged with attenuated WRL-I05 influenza virus. Evidence of viral infection was found in one, two, and two volunteers in each group of IS subjects previously immunized with 400, 100, and 25 IV of vaccine, respectively; in six of the IS volunteers given 5.0 IV of vaccine; and in lOaf 15 control subjects. The results suggest that equivalent immunity was induced in volunteers given ⩾25 IV of vaccine.