Inactivated vaccines. 1. Volunteer studies with very high doses of influenza vaccine purified by zonal ultracentrifugation.

were given safely to more than 5000 volunteers drawn from adolescent, middle aged and elderly populations. The relative paucity of reactions, compared with those groups receiving much lower doses of formalin-inactivated vaccine produced by Sharples centrifugation, suggests that reactions are due to non-viral substances rather than to toxic properties of the viruses, and that these substances are removable. Homologous serum HI antibody responses increased with increasing vaccine dosage and there was