BACKGROUND:
The 2013–2016 Ebola virus outbreak in West Africa was the most widespread in history. In response, alive attenuated recombinant vesicular
stomatitis virus (rVSV) vaccine expressing Zaire Ebolavirus glycoprotein (rVSVΔGZEBOV-GP) was evaluated in humans.

METHODS:
In a phase 1, randomized, dose-ranging, observer-blind, placebo controlled
trial, healthy adults aged 18–65 years were randomized into 4 groups of 10 to receive one of 3 vaccine doses or placebo. Follow-up visits spanned 180 days postvaccination for safety monitoring, immunogenicity testing and any rVSV virus shedding.

RESULTS:
Forty participants were injected with rVSV∆G-ZEBOV-GP vaccine (n = 30) or saline placebo (n = 10). No serious adverse events related to the
vaccine or participant withdrawals were reported. Solicited adverse events during
the 14-day follow-up period were mild to moderate and self-limited, with the exception of injection-site pain and headache. Viremia following vaccination was transient and no longer detectable after study day 3, with no virus shedding in saliva or urine. All vaccinated participants developed serum immunoglobulin G (IgG), as measured by Ebola virus envelope glycoprotein-based enzymelinked immunosorbent assay (ELISA). Immunogenicity was comparable across all dose groups, and sustained IgG titers were detectable through to the last visit, at study day 180.

INTERPRETATION:
In this phase 1 study, there were no safety concerns after a single dose of rVSV∆G-ZEBOV-GP vaccine. IgG ELISA showed persistent high titers at 180 days postimmunization. There was a period of reactogenicity, but in general, the vaccine was well tolerated. This study provides evidence of the safety and immunogenicity of rVSV∆G-ZEBOV-GP vaccine and importance of its further investigation.