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Experts from the Partnership for Research on Ebola VACcination report on progress and uncertainties regarding a safe and effective Ebola vaccine.
Recent Ebola outbreaks, such as the two outbreaks in the Democratic Republic of the Congo (DRC) in 2018, suggest that the virus remains a public health risk. Despite recent advancements in experimental vaccines, critical questions remain unanswered regarding safety and efficacy of these vaccines.
Experts from the Partnership for Research on Ebola VACcination (PREVAC), an international Ebola research consortium, have assessed the current status of Ebola vaccine candidates and clinical trials to highlight important gaps in knowledge to be addressed by future research. In a viewpoint article published in The Lancet on Aug. 10, 2018, PREVAC members observed the 36 trials of Ebola vaccine candidates that have been completed and another 14 that are active, according to clinicaltrials.gov.
The article, “Prevention of Ebola Virus Disease Through Vaccination: Where We Are in 2018”, discusses the need for more data in pregnant women, children, and immunocompromised populations, including the elderly and people infected with HIV. The authors state that more investigation is needed into the durability and rapidity of immune responses generated by various vaccine approaches. The experts also call for studies to identify reliable correlates of protection (the specific and measurable part of an immune response that would indicate protection from Ebola) as well as large-scale trials to fully evaluate the safety and efficacy of experimental vaccines.
The rVSV-ZEBOV experimental vaccine, developed by Merck & Co. and deployed in DRC in May 2018, is the only candidate with some clinical efficacy data, which were obtained in a clinical trial in Guinea conducted during the 2014Â–2016 Ebola outbreak in Guinea, National Institutes of Health (NIH) reports. In the article, the experts also review the status of four additional vaccine candidates under study-Ad26.ZEBOV, MVA-BN-Filo, chAd3-EBO-Z, and the GamEvac-Combi vaccine-and highlight areas where more research is needed.
The authors stress the value of incorporating social science research in clinical trial design to help build trust and engagement with affected communities. They also note that, in addition to examining various vaccines and vaccination strategies to respond more efficiently to future outbreaks, improving the global capacity to conduct clinical research and forming collaborative partnerships such as PREVAC are crucial for success.
The partnership, established in 2017, includes experts from the National Institute of Allergy and Infectious Diseases, part of the NIH, the French National Institute of Health and Medical Research, the London School of Hygiene & Tropical Medicine, the West African Clinical Research Consortium, and their collaborators. NIH states that PREVAC is currently conducting a Phase II clinical trial in Guinea, Liberia, Sierra Leone, and Mali to evaluate three Ebola vaccination strategies in people ages one year and older.