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March 3, 1951


JAMA. 1951;145(9):650. doi:10.1001/jama.1951.02920270044016

According to Horsfall1 and associates of the Rockefeller Institute, the influenza B virus isolated in the New York area during the 1950 epidemic was so different from previous strains as to throw doubt on the desirability of continuing the use of the routine Lee strain exclusively in prophylactic immunization. Using the chick embryo technic, the Rockefeller Institute physicians isolated four strains of influenza B virus from hospitalized patients. They had for comparison the routine Lee virus and five strains isolated by the same technic during previous epidemics (1945, 1947, 1949). Antigenic analyses were made by means of strain specific rabbit, hamster and ferret antiserums. With the rabbit antiserums the nine strains were qualitatively identical but showed decided quantitative differences. One antiserum, for example, contained 1,024 inhibiting units when tested against the 1947 strain, but had only 96 units when tested against the 1950 virus. Qualitative differences, however, were noted