PROPHYLACTIC EFFECT OF LIVE INFLUENZA VACCINE IN A SMALL EPIDEMIC OF INFLUENZA AND ITS EVALUATION METHOD

Field trials were carried out on combined live influenza vaccine A2 and B in November and December, 1965. Febrile reactions were observed in 145 persons (1.31%) of 11.089 vaccinated. A local catarrhal sign was negligible. Antibody response to influenza vaccine A2 was shown by nine (64.0%) of 14 persons with low initial titers. No antibody response was observed to influenza vaccine B because of high initial antibody titers. A small epidemic of influenza A2 occuured in Febraury and March, 1966. Coefficient of effectiveness was 1.14-1.28. Mean maximum fever of epidemic influenza was 37.81 and 37.95°C for the vaccinated and unvaccinated persons, respectively, and the mean number of absent days of infected persons was 1.97 and 2.38, respectively, Ratio of mean absend days of the unvaccinated to vaccinated persons was 1.10-1.42. Ratio of mean absent rate of the unvaccinated control to vaccinated person against influenza was 1.3-1.9. Discussion was made on preferability of using this ratio to evaluate the effect of influenza vaccine.