New Formula for Ebola Vaccine Proves Effective

Highlights

• Ebola virus disease, also known as Ebola hemorrhagic fever, is a disease caused by a virus.
• An newly developed Ebola virus disease (EVD) vaccine increases antibodies 6 months after immunization.
• The vaccine contains vesicular stomatitis virus which was well-tolerated with no safety concerns.

After the ebola outbreak in 2014, there has been lot of research for the development of a vaccine to prevent the disease. An Ebola virus disease (EVD) vaccine, developed in Canada, was well-tolerated with no safety concerns in the phase 1 randomized controlled trial. High antibodies were present in participants 6 months after immunization.

The research team conducted the clinical trial "as part of a coordinated, international effort to expeditiously evaluate candidate EVD vaccines and make them available to control the epidemic," writes lead author Dr. May ElSherif, Canadian Center for Vaccinology, IWK Health Centre, Halifax, Nova Scotia, with coauthors.

Clinical Trial For Ebola Vaccine

The trial involved 40 healthy people aged 18 to 65 years and looked at safety of the vaccine and the lowest dose required for an immune response after injection with one of 3 doses.

At a ratio of 3:1, thirty participants received the vaccine and 10 received placebo injections. The researchers found that adverse events were mild to moderate, with only 3 severe reactions, including headache, diarrhea and fatigue, which completely resolved.

"The results of this trial were positive and very promising; all 3 dose levels of the VSV [vesicular stomatitis virus] Ebola vaccine were well-tolerated by participants, and no safety concerns were identified," says Dr. May ElSherif.

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Several Ebola vaccine candidates are being assessed in ongoing or recently completed phase 1, 2, and 3 trials in various parts of the world. This VSV-Ebola vaccine (formal name: rVSV?G-ZEBOV-GP) was developed at the Canadian National Microbiology Laboratory of the Public Health Agency of Canada. A similar parallel trial was conducted at the Walter Reed Army Institute of Research (WRAIR) in the United States.

Wild type VSV primarily infects animals (e.g., cattle and horses) and rarely infects humans. An upcoming study at 2 sites in Africa, as well as in Montréal and Ottawa in Canada, will test the safety and protection levels of the VSV-Ebola vaccine in HIV-infected adults and adolescents. A completed phase 3 trial showed that the vaccine is effective in preventing EVD in contacts of recently confirmed cases.

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Given the ongoing presence of Ebola, "these facts underscore the importance of continuing efforts and collaborations that may ultimately lead to licensed Ebola vaccines that would protect humans and prevent or control outbreaks in the future," conclude the authors.

Other Tested Vaccines

• The vaccine, called rVSV-ZEBOV, was studied in a trial involving 11,841 people in Guinea in 2015.  Around 5,837 people received the vaccine and no cases of Ebola were recorded 10 days or more after vaccination.
• Dengue and Ebola virus infections were inhibited by using a combination of two cancer drugs in mice. Erloitinib and sunitinib drugs which are approved by the Food and Drug Administration for the treatment of cancer was tested. About half of the mice which received the drug combination was found to survive.
• Chinese Ebola vaccine is the first based on the Ebola virus strain responsible for the West African outbreak in 2014. It is in the form of a freeze-dried powder which will keep it stable for at least two weeks in temperatures of up to 37°C. The vaccine was proved safe in humans.

Reference

1. Author May S. ElSherif et al., Assessing the safety and immunogenicity of recombinant vesicular stomatitis virus Ebola vaccine in healthy adults: a randomized clinical trial, Canadian Medical Association Journal (2017) http://dx.doi.org/10.1503/cmaj.170074.

Source-Medindia