2016 was a tumultuous year in many respects, but it ended with a major victory against Ebola hemorrhagic fever.  Ebola’s most recent outbreak ravaged West Africa from 2013 to 2016, killing roughly two out of every five patients and tens of thousands of people in total.  Treatment options are limited once the disease takes hold, so researchers have been pursuing a vaccine that protects against infection.  These efforts have produced rVSV-ZEBOV, a vaccine that was recently found to be 100% effective in preventing Ebola infection during a two-year clinical trial that comprised nearly six thousand individuals.

While similar, the new Ebola vaccine isn’t quite the same as your annual flu shot.  Many vaccines contain either an inactivated or weakened form of the corresponding virus to train your immune system to recognize the full-strength pathogen.  Ebola virus, however, is so dangerous that only a small piece of it was included in rVSV-ZEBOV.  This eliminates any safety concerns, but it may limit the vaccine’s long-term protective capabilities because the immune system is never exposed to the entire infectious agent.

Another important difference is that rVSV-ZEBOV can only be used when an outbreak is already taking place.  Routine, preventative vaccines—like the flu shot—typically exhibit mild and infrequent side-effects, but rVSV-ZEBOV can cause serious adverse reactions due to its unconventional composition.

Despite these drawbacks, an effective Ebola vaccine is a tremendously important weapon in our arsenal for combatting future outbreaks.  Just don’t expect CVS to stock it anytime soon.

Acknowledgments: Many thanks to Shirlee Wohl, a graduate student in the Systems Biology Program at Harvard University, for providing her expertise and commentary on the topic.

Managing Correspondent: Christopher Gerry

Original Research: Efficacy and effectiveness of an rVSV-vectored vaccine in preventing Ebola virus disease: final results from the Guinea ring vaccination, open-label, cluster-randomised trial (Ebola Ça Suffit!)
– The Lancet

Media Coverage: New Ebola Vaccine Gives 100 Percent Protection – The New York Times; Ebola vaccine gives 100% protection, study finds – CNN;  The new ‘100% effective’ Ebola vaccine owes a debt to the scientists who beat smallpox – The Conversation