Antibody response and persistence in volunteers following immunization with varying dosages of a trivalent surface antigen influenza virus vaccine.

The serum antibody responses and 50% protective levels (PL50) of antibody were determined, using the SRH test, at one and twelve months post-vaccination in a group of student volunteers immunized with one of three dosages of a trivalent surface-antigen influenza virus vaccine, or with placebo. It was found that, for the H3, H1 and B haemagglutinin components present in the vaccine, a dose of 6 micrograms HA elicited high serum antibody responses at one month post-immunization. High mean antibody levels and a high incidence of volunteers with PL50 values of antibody against each of the HA components of the vaccine remained in the volunteer group twelve months later. The results are discussed in relation to the vaccine dosage used and the nature of the population immunized.