Serological responses in volunteers to inactivated trivalent subunit influenza vaccine: antibody reactivity with epidemic influenza A and B strains and evidence of a rapid immune response.

A study of the immunogenicity of the inactivated trivalent subunit influenza vaccine for the 1989/90 season was performed in what proved to be an influenza epidemic year. One hundred student volunteers at The London Hospital Medical College participated in the study and the findings indicated that there was an excellent serological match between the epidemic strain of influenza A (H3N2) and the vaccine strain. Before vaccination, the geometric mean titre (GMT) to A/England/308/89, a representative H3N2 epidemic strain in the United Kingdom from the 1989/90 season, was 46. Post-vaccination the antibody levels rose and 99% of vaccinees had HI titres of greater than or equal to 40, the GMT being 131. The serological responses were also investigated against other circulating influenza A (H3N2 and H1N1) and B strains. Preliminary results of an evaluation of the rapidity of the immune response showed that in three of six subjects rises in HI antibody appeared within two days of vaccination.