by The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission. Over the past decade, multiple Ebola outbreaks have occurred in Africa causing thousands of deaths. Consequently, there has been an urgent need to develop a safe and effective vaccine to prevent future outbreaks. Significant progress has been made in vaccine development and several candidate vaccines have entered clinical trials. This article provides an update on the current status of Ebola vaccine development and trials.
Early Vaccine Candidates
Initial efforts to develop an Ebola vaccination started in the 1990s following major outbreaks in Democratic Republic of Congo and Gabon. A number of vaccine candidates were tested in non-human primates with varying success rates. rVSV-EBOV and ChAd3-EBOV were found to fully protect non-human primates from infection and disease after a single dose. The Ad5-EBOV and DNA-EBOV vaccines conferred partial protection. These vaccine candidates showed promise and warranted further investigation and clinical testing in humans.
Phase 1 Trials
The first-in-human Phase 1 Ebola Vaccine clinical trials began in North America and Africa in the 2000s. These initial trials evaluated vaccine safety and ability to generate an immune response in healthy adults. The rVSV-EBOV vaccine was the first candidate tested in a Phase 1 trial with encouraging results. It produced antibodies in over 90% of recipients and had a good safety profile with only mild to moderate adverse effects. Meanwhile, Phase 1 trials of the ChAd3-EBOV, Ad5-EBOV and DNA-EBOV vaccines also showed favorable safety data and immunogenicity. No serious adverse events occurred in any of these trials.
Scale-Up During 2013-2016 Outbreak
The largest recorded Ebola outbreak started in West Africa in 2013 and spread rapidly across Guinea, Liberia and Sierra Leone between 2013 to 2016. This outbreak catalyzed new research efforts and prompted fast-tracking of Ebola vaccine trials. In an effort to curb the spread, a ring vaccination clinical trial was conducted in Guinea in 2015 to test the rVSV-EBOV vaccine’s effectiveness. People who had contact with an Ebola patient received the vaccine. No further cases occurred among the over 11,000 vaccinated individuals, demonstrating 100% efficacy.
Based on this compelling evidence, the rVSV-EBOV vaccine received regulatory approval for use from European and African national regulators in emergency situations. Over 160,000 doses were distributed to help bring the 2013-2016 West African outbreak under control. Meanwhile, other vaccines such as ChAd3-EBOV and Ad26.ZEBOV/MVA-BN-Filo also continued Phase 1 and 2 trials during this period to expand the vaccine pipeline. However, rVSV-EBOV remains the only approved preventive vaccine for Ebola virus disease at present.
Late-Stage Confirmatory Trials
Following the successful emergency use of rVSV-EBOV vaccine, large late-stage efficacy trials were urgently conducted in West Africa and DRC to gather more confirmatory evidence. In 2019, interim results revealed continued 100% protection in over 18,000 individuals enrolled in Guinea and DRC prevention trials. The vaccine also demonstrated safety and tolerability similar to earlier trials. Final analyses ongoing to demonstrate long-term protection duration before worldwide WHO prequalification and broader distribution. ChAd3-EBOV and Ad26.ZEBOV/MVA-BN-Filo are still undergoing Phase 2 and 3 efficacy tests as additional options for disease prevention.
Significant strides have been made in developing vaccines against the deadly Ebola virus in the past decade. The rVSV-EBOV vaccine has proven highly effective at preventing disease based on ring vaccination and late-stage efficacy trials. Approval is pending final confirmatory data. Besides rVSV-EBOV, other candidates are also being evaluated that could diversify vaccine options. Moving forward, WHO prequalification is required for wider global use. Roll-out infrastructure needs strengthening in Africa. Research continues on improving vaccines further, developing combination vaccines against related viruses and building capacity to rapidly respond to future Ebola outbreaks. Overall, advances in Ebola vaccine development bring hope for better control and potential elimination of this devastating disease.
*Note:
1.Source: Coherent Market Insights, Public sources, Desk research
2.We have leveraged AI tools to mine information and compile it
About Author - Ravina Pandya
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