Inactivated influenza virus vaccines in man: a comparative study of subunit and split vaccines using two methods for assessment of antibody responses.

The serum antibody responses and reactions of volunteers to a trivalent subunit influenza virus vaccine prepared using cetyl trimethyl ammonium bromide (CTAB) or trivalent split vaccine prepared by ether-extraction, were essentially similar, although the antibody levels to the A/Brazil/78 (H1N1) components of the vaccine were greater in volunteers receiving the subunit preparation. Antibody responses to the vaccines were assessed using both the haemagglutination-inhibition (HI) and single radial haemolysis (SRH) tests. Although good correlation was found between the tests with respect to both antibody titres in individual sera and antibody responses in serum pairs to both A(H3N2 and H1N1) and B influenza viruses, the greater reliability of SRH, indicates this test should supplant the HI test for the routine measurement of antibody responses to influenza viruses.