The epidemic of Asian influenza began in Japan in May 1957, reaching a peak towards the end of June, subsiding, and showing a second, equally serious, wave in November-December. The method and place or places of its introduction into the country are not clear, but the important role of schoolchildren in its spread seems well established. While the average attack-rate for the country as a whole was some 26% in the first epidemic wave, it was as high as 50%-60% in concentrated communities such as schools and military camps. The severity of the illness was not very great in the population as a whole, but the death-rates among infants and the aged were remarkably high. The main causes of death were acute pneumonia and cardiac insufficiency. Vaccination of the general population was not carried out on a wide scale.

Death↗

PubMed1959

Human vaccination experiments with Asian influenza vaccine in Japan.

Details are given of a number of experiments, carried out in 1957 in Japan among high school students, factory workers and student nurses and in military camps, to test the efficacy of Asian influenza vaccine at various strengths and doses and prepared from different virus strains. The Asian influenza virus strains used were A/Adachi/2/57, A/Kumamoto/Y5/57 and A/Kumamoto/K9/57. Results were tested by the haemagglutination-inhibition reaction.Antibody response to Adachi-strain vaccine was very satisfactory, particularly when inoculated at a strength of 300 CCA units per ml in two doses of 0.5 ml each. Monovalent Adachi-strain vaccine gave better results than a trivalent vaccine containing Adachi strain, an earlier A strain and a B strain in equal amounts. Vaccine prepared from the Y5 strain, considered representative of extreme Q-phase virus, was less effective than Adachi vaccine.

Antibody Formation↗

PubMed1959

Studies on the P-Q phases of A/Asia/57 influenza viruses.

Some 300 strains of A/Asia/57 influenza virus were tested for haemagglutination-inhibition against normal human convalescent serum and showed wide variations; some, indeed, were not inhibited at all. The same strains, when tested against rooster antisera obtained by immunization with one of three strains (Adachi, K9 and Y5), again showed considerable variation in their degree of haemagglutination-inhibition. These two series of variations were fairly closely correlated.Eight strains considered representative of the range of inhibition variation were further tested against a number of human convalescent sera and against sera from persons inoculated with monovalent Adachi vaccine; the results indicated that the order of variation did not change.Neutralization tests to determine the immunizing potency of vaccines prepared from Adachi, K9 and Y5 strains showed that Adachi vaccine had far the greatest immunogenicity and that K9 was slightly more potent than Y5. Mouse adaptation of Y5 strain considerably enhanced its immunizing potency, but did not alter its reaction to human convalescent serum.

Animals↗

PubMed1958

Epidemiological studies of A/Asia/1957 type influenza in a nursery near Tokyo City.

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Epidemiologic Studies↗