Evaluation of Monovalent Influenza Vaccine in a Retirement Community During the Epidemic of 1965-1966

Monovalent adjuvant and aqueous influenza vaccines were evaluated in a retirement community from 1964 to 1966. In the second year of investigation, an epidemic of A2 influenza provided opportunity to study the protective value of immunization. Vaccine efficacy was shown to be related to the pattern of vaccination. Individuals who had received single doses of A2 vaccine in both years of the study were considerably better protected than those who had received vaccine in only one of the years. The rate of febrile illnesses in the former group was more than 90% below that of vaccinated control. Those given one dose were only about half as well protected. Monovalent adjuvant A2 vaccine given more than a year before the outbreak appeared to protect as well as, if not slightly better than, monovalent aqueous vaccine administered several months before the epidemic.