The efficacy of live and inactivated vaccines of Hong Kong influenza virus in an industrial community. A report to the Medical Research Council Committee on influenza and other respiratory virus vaccines.

Intranasal vaccines of inactivated or living attentuated A2/Hong Kong influenza viruses were compared for clinical acceptability, serological effects and protective efficiency against natural epidemic influenza in a large industrial and clerical population.Neither vaccine resulted in any significant untoward side-effects. The serum haemagglutination-inhibiting (HI) antibody response within 1 month of vaccination was similar with both vaccines; approximately 50% of those with little or no pre-vaccination antibody developed 4-fold or greater rises in titre. The effect of the antigenic potency of the vaccines and the prior immunological experience of the population is discussed. Volunteers given live vaccine showed a 2.2-fold lower incidence of clinical influenza than those given killed vaccine in a natural epidemic 16 months after vaccination.