MEASURING THE EFFICACY OF VACCINATION IN AFFORDING PROTECTION AGAINST PLAGUE

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 57  (2) , 309-313
Abstract
The relationship of F1 [fraction 1] antibody titer to protection against plague was investigated by subjecting seropositive laboratory rats to virulent challenge and observing for survival. The passive hemagglutination (PHA) test in microtiter was employed for serology. Rats vaccinated with live vaccine EV76(5lf), killed USP vaccine or F1 antigen and challenged by s.c. inoculation of 1 .times. 103-5 .times. 105 Yersinia pestis survived at similar rates that, overall, equalled 6% at titers less than 1:16, 46% at titers of 1:32-1:64, 90% at titers of 1:128-1:256 and 96% at titers of 1:512-1:1024. Rats vaccinated with F1 antigen and rats infected previously were challenged intranasally with 8.9 .times. 104 Y. pestis and subsequently demonstrated similar rates of survival that was zero at titers less than 1:128, 86% at titers of 1:128-1:256 and 100% at titers of 1:512-1:1024. The significance of titer of F1 antibody as a measure of seroimmunity against acute bubonic or pneumonic plague is discussed for rats, monkeys and man.