PROTECTIVE EFFICACY OF A LIVE ATTENUATED VACCINE AGAINST ARGENTINE HEMORRHAGIC-FEVER

Argentine hemorrhagic fever (AHF), caused by the arenavirus Junin, is a major public health problem among agricultural workers in Argentina, A prospective, randomized, double-blind, placebo-controlled, efficacy trial of Candid 1, a live attenuated Junin virus vaccine, was conduct ed over two consecutive epidemic seasons among 6500 male agricultural workers in the AHF-endemic region. Twenty-three men developed laborato ry-confirmed AHF during the study; 22 received placebo and 1 received vaccine (vaccine efficacy 95%; 95% confidence interval [CI], 82%-99%). Three additional subjects in each group developed laboratory-confirme d Junin virus infection associated with mild illnesses that did not fu lfill the clinical case definition for AHF, yielding a protective effi cacy for prevention of any illness associated with Junin virus infecti on of 84% (95% CI, 60%-94%). No serious adverse events were attributed to vaccination, Candid 1, the first vaccine for the prevention of ill ness caused by an arenavirus, is safe and highly efficacious.