Candid No. 1 Argentine Hemorrhagic Fever Vaccine Protects against Lethal Junin Virus Challenge in Rhesus Macaques

The protective efficacy of Candid No.1, a live-attenuated vaccine against Argentine hemorrhagic fever AHF, was evaluated in non-human primates. Twenty rhesus macaques immunized 3 months previously with graded doses of Candid No. 1 16 -127, 000 PFU, as well as 4 placebo-inoculated controls, were challenged with 4.41 log10 PFU of virulent P3790 strain Junin virus. All controls developed severe clinical disease 3 of 4 died. In contrast, all vaccinated animals were fully protected none developed any signs of AHF during a 105-day follow-up period. Viremia and virus shedding were readily detected in all placebo-vaccinated controls, while virus could be recovered only once by amplification from throat swabs of 2 Candid No 1 vaccinees on day 21.