Seroepidemiological Studies on the Effect of Influenza Vaccine. : —Special Reference to the Character of the Subject Population—
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概要
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From a seroepidemiological point of view a survey was conducted on the effect of influenza vaccine over a representative epidemic period of influenza of type A and B extending from August, 1968, when Hongkong type A appeared, and March, 1979. The results obtained are summarized as follows.1. The rate of infection in each epidemic was 30.6% for the A/Kumamoto /1/72 strain, 46.1% for the B/Kanagawa/3/76 strain, and 46.4% for the A/Tokyo/1/77 strain. It was only 8.7% in the second epidemic of the A/USSR/92/77 strain.2. The rate of infection was analyzed by HI antibody titer before the epidemic. As a result, it was 8% or less, showing no marked fluctuation, in every epidemic, so long as the patients possessed antibody titers of 1:641:128 or more against the epidemic strain.3. When the patients were examined for the production of antibody higher than 1:128 in titer against the initial vaccine strain, only about 20% of them exhibited such production as this against Hongkong type A and USSR type A.4. On the other hand, only about 710% of the patients exhibited such production as this against type B.5. Patients of the population exposed to the first epidemic of the A/USSR/92/77 strain were inoculated with vaccine containing virus of this strain. Then they were involved in the second epidemic of this strain. As a result, they presented such a low rate of infection as 8.7%.6. Examination was carried out on medical workers in offices and plants where epidemics of Hongkong type A and USSR type A had confirmed. None of them were found infected when they were examined for HI antibody against Hongkong type A after inoculation with vaccine and for retained antibody against USSR type A. In conclusion, it can be expected that influenza vaccine will have an effect when the strain used for the vaccine is identical with that which has caused the respective epidemic. The existing method of inoculation with vaccine cannot be anticipated to be effective when an antigenic shift strain or antigenic drift strain showing a large variation appear in future. It can be well expected, however, from the present studies that influenza vaccine will display an effect in those cases by increasing the number of inoculation or by raising the amount of virus contained in the vaccine.