Single-Dose Monovalent A2/Hong Kong Influenza Vaccine

Authors:
  • HFHjordis M. Foy
    Hjordis M. Foy
  • MCMarion K. Cooney
    Marion K. Cooney
  • RMRuth McMahan
    Ruth McMahan
  • EBEva Bor
    Eva Bor
  • JGJ. Thomas Grayston
    J. Thomas Grayston
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Abstract
A controlled field study to evaluate the efficacy of a single dose of monovalent influenza A2/Hong Kong vaccine was conducted among Seattle area school children in late fall of 1968. Concurrent epidemics of influenza A and influenza B occurred from December 1968 through February of 1969. Approximately 14 months after administration of vaccine, an epidemic of influenza due to A2/Hong Kong strain occurred in this same population, with the epidemic peak in January 1970. This afforded us the opportunity to examine the long-term effect of the vaccine. Protection lasting 14 months after immunization was evident by (1) significantly less absenteeism from school, (2) 58% reduction of reported influenza-like illness, (3) 72% to 76% reduction in infection rates as estimated by serologic testing, and (4) 80% to 83% reduction in the rate of serologically confirmed influenza illness.