Leading Ebola Vaccine Candidates

Vincent Pavot*

Leading Ebola Vaccine Candidates

The ongoing outbreak of Ebola Virus Disease in West Africa is the largest
outbreak ever recorded with a total number of 28,602 confirmed, probable, or suspected cases
in Guinea, Liberia, and Sierra Leone, including 11,301 reported deaths since December 2013
(as of January 17, 2016).

A meeting convened by the World Health Organization in
September, 2014, concluded that an urgent unmet need exists for efficacy
and safety testing of the EVD vaccine candidates and that clinical trials should be expedited.

These vaccines could be used both in an outbreak setting
and to provide long-term protection in populations at risk of
sporadic outbreaks.

A number of vaccines have been evaluated in phase 1 trials including DNA vaccines,
virus-like particles and viral vectors, but the two most advanced first-generation
Ebola vaccines candidates are the live replicating Vesicular Stomatitis
Virus and the replication defective chimpanzee adenovirus 3 (ChAd3).

arthralgia in the second week after injection.
Reducing the dose of rVSV-ZEBOV from 10 million (or greater) to 300,000 PFU
improved its early tolerability but lowered antibody (Ab) responses and did not
prevent vaccine-induced arthritis, dermatitis, or vasculitis.

Regarding the induction of specific Abs, the rVSV-ZEBOV vaccine generated
GP-binding Abs in all participants at all
doses (as few as 300,000 PFU may be sufficient), showing its
immunogenicity in humans. In the study undertaken in the US,
Ab titers against the Ebola Zaire GP, at day 28, were higher in
the group receiving 20 million PFU than in the group receiving
3 million PFU.

These data support continued development of
the rVSV-ZEBOV Ebola vaccine candidate in general and the
selection of a dose of 20 million PFU for phase 2 and 3 trials.

Vaccin Res Open J. 2016; 1(1): 1-6. doi: 10.17140/VROJ-1-101