A study volunteer receives inoculation at Redemption Hospital in Monrovia, Liberia, during the opening days of PREVAC, a phase 2 Ebola vaccine trial in West Africa. Photo by: NIAID / CC BY

MANILA — Frontline health workers fighting the Ebola virus in the Democratic Republic of the Congo could be protected from the virus for longer than 12 months, a new study has found.

Funded by the British government, the study was done among healthy volunteers who received a number of vaccines in the United Kingdom between 2014-2016. The vaccines included Merck’s — known as MSD outside the United States and Canada — rVSV-ZEBOV, which was also used in the current outbreak in DRC; GlaxoSmithKline’s ChAd3 EBOV; and Janssen’s AdHu26.

After two-and-a-half years, the study found volunteers still have strong antibody response to the virus.

Katie Ewer, associate professor at the University of Oxford’s Jenner Institute in the United Kingdom, and one of the study authors, said the findings lend insight into how the vaccines could be used in regions at risk of future Ebola outbreaks and to protect health care workers before the risk of infection becomes widespread.

“What we're trying to do with this study is understand how often we need to go and vaccinate these people. So by sharing that we have good persistence of immunity at two or three years, we know that the vaccine lasts at least that long, and we won't have to get back and reboost them,” she told Devex.

“In a country like the DRC, where we know there are likely to be sporadic outbreaks, it would be great to go and vaccinate everybody who's a health care worker …  before an outbreak happens rather than using it reactively like we're doing now,” she added.

And the researchers aren’t stopping there. Their next plan is to give a booster dose to the very people who received the vaccines three years ago and find out how that adds to their immunity to the virus.

“Although we know that these immune responses are persisting, we'd like to know what happens if we give them another dose of vaccine. Would that mean that somebody who receives the vaccines gets protected say for 10 years? That's really important information because if we knew that we only needed to vaccinate, for example, every 10 years, then that massively reduces the cost of administering these type of vaccines to health care workers,” Ewer said.

Other vaccines’ development

The Ebola crisis in West Africa has exposed how unprepared the world is to such outbreaks, leading to an urgency in finding a viable vaccine.

But that urgency has opened up opportunities not just to address Ebola, but also other lethally infectious diseases for which no vaccines are currently available, Ewer said.

In addition to an Ebola vaccine, the Coalition for Epidemic Preparedness Innovations, whose main mandate is to speed up the development of vaccines for infectious disease epidemics, is currently funding the development of vaccines for Lassa fever, Middle East respiratory syndrome, Nipah virus, and coronavirus at the Jenner Institute.

The MERS vaccine is currently in clinical testing in humans and will shortly be in clinical trial in Riyadh, Saudi Arabia, one of the regions most at risk of a MERS outbreak. The Jenner Insitute also recently started clinical trials on a vaccine against Chikungunya, although that is not funded by CEPI.

By using the same technology as the Ebola vaccine — called viral vectors — Ewer explained they can significantly reduce the time it takes to develop vaccines.

“The great thing about viral vectors is … if we're making a vaccine against Lassa fever, for example, all we do is take the Ebola gene out, and put the Lassa gene in. And that means that all of the same technology to do with how we manufacture the vaccine, everything we know about the safety of these delivery systems applies to those vectors, whether it's for Ebola or for MERS or for Nipah. And by ... making vaccines this way, it makes it much quicker and easier to produce new vaccines,” Ewer said.

Given this technology, how long will it take for these vaccines to be available for health workers?

According to Ewer, it will be possible to have them available in a few years. The idea is to generate enough safety data to show that they work and can be used in case of an outbreak.

Merck’s Ebola vaccine was able to demonstrate this, when, even without a license, it was used in DRC under so-called “compassionate use regulations.”

The technology has been around for years, but lack of foresight and funding to develop these vaccines have put their development on hold.

“For diseases like Ebola and Lassa, I think nobody really thought there would be outbreaks on the scale that we saw in 2014. There were some vaccines available, but they haven’t had very much testing in humans. Also, there just really wasn’t the funding available to develop these kinds of vaccines,” Ewer said.

About the author

  • Jenny Lei Ravelo

    Jenny Lei Ravelo is a Devex Senior Reporter based in Manila. She covers global health, with a particular focus on the World Health Organization, and other development and humanitarian aid trends in Asia Pacific. Prior to Devex, she wrote for ABS-CBN, one of the largest broadcasting networks in the Philippines, and was a copy editor for various international scientific journals. She received her journalism degree from the University of Santo Tomas.