Vaccines are a life-saving tool that prevent infection by training your immune system to fight against viruses and bacteria. Canada played a significant role in the creation of an Ebola vaccine.
Ebola virus (EBOV) is a deadly virus found in regions of Africa that causes hemorrhagic fever and has high mortality rates. Work on an Ebola virus vaccine spanned many decades across many countries but has important roots in Canada. Ebola was recognized for its risk of causing a global epidemic and its potential use as a bioterrorism agent. In 2001, the Public Health Agency of Canada’s National Microbiology Laboratory in Winnipeg started to create an Ebola vaccine. At this time, Dr. Heinz Feldman, working at the National Microbiology Laboratory, was trying to understand how the Ebola virus causes disease. He was particularly interested in a protein on the surface of the Ebola virus called the glycoprotein, which enables the Ebola virus to infect host cells. He used the Vesicular Stomatitis Virus (VSV), a virus that normally infects cattle but is not harmful to humans, which can be genetically engineered. Dr. Feldman’s research group successfully created VSV-EBOV, a version of VSV that had the Ebola virus glycoprotein on its surface.
Then Dr. Feldman and his team wanted to see if the VSV-EBOV could act like a vaccine and protect mice from the Ebola virus. They injected mice with the VSV-EBOV and then infected the mice with the Ebola virus. The results were striking; the unvaccinated mice who were infected with Ebola virus died, whereas all the vaccinated mice who then received the Ebola virus survived. This protection was likely due to an immune response against the Ebola virus glycoprotein and was a major breakthrough that led to further research for generating the VSV-based Ebola virus vaccine.
The next step was to test the safety and efficacy of the VSV-EBOV vaccine in non-human primates. A study published in 2005 showed the VSV-EBOV vaccine was safe and effective in preventing infection and death from the Ebola virus in monkeys. However, the progress to create a human vaccine was slow and funding for the Ebola vaccine research was hard to secure in Canada, with other pressing public health needs taking priority. Finally, a switch in funding leadership combined with the promising results in monkeys and strong advocacy from researchers allowed the Canadian scientists to secure half the funding for vaccine development. The scientists in Winnipeg partnered with the company IDT Biologika GmbH in Germany to produce the vaccine on a larger scale. The new vaccine products were once again tested in animals with promising results, so IDT scaled up production of the Ebola vaccine.
In 2013 a large and deadly epidemic of Ebola virus disease started in Guinea and rapidly spread through West Africa. From 2013-2016 the Ebola virus disease killed more than 11,000 people in 30,000 cases. This epidemic revealed the pressing need for human clinical trials of the Ebola vaccine. Many scientists around the world raced to validate the safety and effectiveness of the VSV-EBOV vaccine in humans. One of the first phase 1 studies of the VSV-EBOV vaccine occurred in Halifax, Canada at the Canadian Center for Vaccinology, where healthy adults were vaccinated with either the VSV-EBOV vaccine or a placebo (a saline injection that does not contain any virus). Then they were monitored for adverse reactions and for anti-Ebola antibodies in the blood. The trial successfully showed that the Ebola vaccine was safe and produced an antibody response against the Ebola virus glycoprotein. In addition to Canada’s contribution of creating and testing the Ebola vaccine, the Government of Canada offered 1000 doses of the Ebola vaccine to the World Health Organization (WHO) to test in clinical trials in Africa, and Canada provided more than $100 million in funding to the WHO to support Ebola countermeasures.
During the West African epidemic in 2014 the pharmaceutical company Merck acquired the rights to the VSV-EBOV vaccine to produce it on a larger scale for clinical trials. The next big milestone was a large, randomized control trial in Guinea during the epidemic to test the efficacy of the VSV-EBOV vaccine in the field. This trial was led by the WHO and Norway but had Canadian funding and components. The Guinea trial had a unique and effective strategy called “ring vaccination”: people who had a clinical case of Ebola virus disease were identified by the Ebola response team and all contacts of the infected person and their contacts were identified and randomized 1:1 to either receive the VSV-EBOV vaccine immediately or to receive the vaccine 21 days later (as a control group). The trial enrolled nearly 4,000 people. Remarkably, in people who received the vaccine immediately, zero cases of Ebola virus disease were reported 10 days after vaccination. In contrast, in the delayed vaccine group, 16 individuals had confirmed Ebola virus disease. The vaccine was 100% effective in preventing Ebola virus disease in this clinical trial, paving the way for the vaccine to be licensed and approved. This trial might have also helped preventing community infections in Guinea.
In 2019 the WHO gave pre-authorization to the VSV-EBOV vaccine, which allowed it to be used to fight outbreaks in the Democratic Republic of Congo and Guinea in 2020 and 2021, respectively. The VSV-EBOV vaccine was approved by the FDA in the United States in 2019 and was also authorized for use in Canada. However, the vaccine is not part of the regular immunization recommendations for Canadians because Ebola virus disease is very rare in Canada. Rather it can be used to treat someone immediately after they have been exposed to the Ebola virus, such as a health care worker treating a patient with the Ebola virus disease. Worldwide, more evidence has recently accumulated from clinical trials that the Ebola vaccine is safe and effective in creating antibody responses against the Ebola virus. The Ebola vaccine developed in a Canadian lab now can save lives in emerging outbreaks of the Ebola virus disease globally.
Beth DeConinck
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- Canada’s Role in the Creation of the Ebola Vaccine - October 4, 2024
