The first human trials of a designed-in-Canada Ebola vaccine suggest it is safe and triggers a rapid immune response, studies published Wednesday reveal.
The work, based on six different clinical trials in the United States, Switzerland, Germany, Gabon and Kenya, found the vaccine quickly generates antibodies in people who receive it. Whether those antibodies protect against infection remains to be seen, but early evidence suggests that is a strong possibility.
The vaccine is called rVSV-ZEBOV and was designed by scientists at the National Microbiology Laboratory in Winnipeg, part of the Public Health Agency of Canada. It is being developed by U.S. biotech NewLink Genetics and pharma giant Merck.
Published in the New England Journal of Medicine, the research describes Phase 1 clinical trials and shows for the first time what happens when this vaccine is given to a number of people.
Phase 1 trials are designed to show if an experimental product is safe and to help determine what an appropriate dose should be. They are too small to answer the question: Does this vaccine work?
It is hoped the answer will come from larger Phase 3 trials currently underway in West Africa.
The research, grouped into two reports, shows people who received the vaccine started to generate antibodies quickly. That is an attractive feature in a vaccine that would be used to quell future Ebola outbreaks, if it makes it through the licensing process.
“There were pretty positive signals of immunogenicity at 14 days post vaccination across both of the (vaccine) doses that are reported,” said Col. Stephen Thomas, a senior author of the article describing the findings of the two U.S. trials. Those two trials were conducted at the Walter Reed Army Institute of Research and the U.S. National Institute of Allergy and Infectious Diseases, both located in Bethesda, Md.
By Day 28, all the vaccinated volunteers had shown an antibody response.
The article reporting on data from the European and African trials revealed that blood from vaccinated subjects contained antibodies that neutralized or killed Ebola virus — a finding that adds weight to the belief that this vaccine should protect against infection.
The vaccine often induces side-effects such as fever, muscle aches and even arthritis-like joint pain on occasion. But the side-effect profile was deemed to be acceptable, especially given the lethality of the disease the vaccine aims to protect against.
The combined work also points to a pattern of side-effect development that may relieve some experts who had worried about using the vaccine in a setting where Ebola actually circulates. They have been concerned that a vaccine that induces fever might make it more difficult to detect Ebola infections early, given that fever is often the first sign of disease. Early detection of cases is key to efforts to stop transmission.
The research teams found that fevers, when they occurred, happened early and resolved quickly.
That should make it easier for people running the trials in West Africa to distinguish vaccine-triggered fevers from Ebola-induced ones, suggested Dr. Claire-Anne Siegrist, the principle investigator for the European and African trials.
“You tell people, ‘Look, if you have fever tomorrow, this is the vaccine. But if it lasts for more than two days, you come and see us immediately.’ That’s quite easy,” she said.