Finbarr O’Reilly/The New York Times

December 2, 2019

Ebola’s Expiration: Merck’s Ebola Vaccine Approved in Europe

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Researchers, healthcare providers and global health officials who worked hard to grapple with the devastating Ebola outbreak of West Africa between 2014 and 2016 can finally breathe a sigh of relief — the very first Ebola vaccine was finally approved in Europe.

Known as Ervebo, this Ebola vaccine is manufactured by the biopharmaceutical company Merck and was granted marketing authorization by the European Commission on November 11. Prof. Gary Whittaker, virology, shared his insight on the inner workings of the vaccine and its development, as well as what this landmark achievement means for the future of global health.

Whittaker explained that the vaccine itself is actually a recombinant virus, based on the backbone of vesicular stomatitis virus originating from sheep and goats.

“[VSV] is very efficiently growing and relatively easy to make, [so] it’s engineered to express the glycoprotein of Ebola … it generates the immune response against the Ebola virus glycoprotein, which is equivalent to the surface protein of Ebola,” Whittaker said. Because the immune system generates antibodies against the Ebola surface proteins, it creates protection against the Ebola virus itself.

Whittaker also said that the vaccine is a ring vaccine, which means that people usually won’t get it as an infant. “What’s happening here is that the vaccine is employed in primary and secondary contacts of Ebola-infected people. It’s more of a short-term way of preventing transmission,” Whittaker said.

Since vaccinating the entire West African population would be impractical, Whittaker said the vaccine would be reserved for healthcare workers and other people coming into direct contact with the virus.

“This vaccine gives very quick, robust immunity, and the virus itself is relatively slow in transmitting, so the two things together will allow this ring vaccination protocol to actually work,” Whittaker said.

Whittaker went on to explain that although the famous Ebola outbreak has long since ended, there will almost certainly be future outbreaks, and this vaccine will be very useful in managing them. “It will almost be a recurrent theme every few years, and it’s just a case of where it happens and how bad it’s going to be,” Whittaker said.

The approval of the vaccine in Europe is also a major step in establishing a stockpile of the vaccine by an alliance called Gavi. “Gavi will maintain a stockpile for the rapid deployment for whatever country needs it, so it’s not dependent on any one country to stockpile or purchase the vaccine — it’s a global NGO that can act immediately whenever the need arises,” Whittaker said.

However, the vaccine has its limitations. Whittaker explained that although the vaccine provides short-term protection from the Ebola virus, it’s not clear how long that immunity lasts, and what exactly is necessary for long-term protection is unclear.

Furthermore, the vaccine only protects against the Zaire species of Ebola. Although switching out the strain to create new vaccines for the other circulating strains would be relatively simple, each new vaccine would have to undergo the entire approval process.

However, Whittaker is very optimistic about the global impact of the vaccine. “It sets up this real ability to come in and block the transmission really early to prevent recurrences that happen in West Africa with all the destruction that caused, and it can really protect the health care workers that go in,” Whittaker said.

“Thankfully a lot of prior work in developing these [vaccines] could be applied to the need in a relatively rapid fashion. It doesn’t seem very rapid, but for a vaccine, it’s actually pretty rapid for this to be out there and available,” Whittaker said.