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Ebola Vaccine Appears Safe, Effective in New Studies

Scientists report ‘robust’ antibody production

Early-stage trials of an experimental Ebola vaccine, two in the U.S. and four in Africa and Europe, have found that it triggered “robust” production of Ebola-fighting antibodies and appears to be safe, according to a report from Reuters.

Since trials cannot ethically expose volunteers to Ebola, the production of antibodies is a proxy for whether vaccines could prevent or even treat the disease.

There is currently no vaccine or specific treatment for the Ebola virus, which has killed more than 10,000 people in West Africa since last spring, according to the World Health Organization. It is the worst Ebola epidemic in history but finally appears to be abating.

The trials all tested a vaccine called VSV- ZEBOV, which was developed at the Public Health Agency of Canada and licensed to Merck. It consists of a cattle virus –– recombinant vesicular stomatitis virus (rVSV) –– that has been engineered to carry Ebola genes, which produce proteins meant to trigger the production of anti-Ebola antibodies.

According to separate teams of scientists, that is what happened, two papers in the New England Journal of Medicine reported.

In the U.S. trials, conducted at the National Institutes of Health (NIH) and the Walter Reed Army Institute of Research starting last October, 52 healthy adult volunteers received single injections of saline or either of two doses of vaccine.

The most common adverse effects, such as injection-site pain and temporary fever, were mild. All 40 participants who received vaccine produced anti-Ebola antibodies within 28 days, with most responding sooner.

The higher dose tripled the antibody response of the lower dose. The “robust” response to a single dose “could be particularly useful in outbreak interventions,” said Walter Reed’s Col. Stephen Thomas, senior author of the U.S. paper.

The higher dose is being tested in a larger trial in Liberia. Partly through that trial, both VSV- ZEBOV and an experimental vaccine from GlaxoSmithKline called cAd3-EBOZ “appear to be safe,” the NIH announced last week. The other studies were similarly encouraging.

In coordinated trials in Germany, Switzerland, Gabon, and Kenya, 158 healthy volunteers received placebo or any of five dose-levels of the VSV-ZEBOV vaccine.

Although the Geneva study was temporarily halted last year after 11 of 51 participants developed arthritis, overall there were “no serious vaccine-related adverse events,” the researchers reported. All 150 people who received vaccine developed antibodies to Ebola, with higher responses to higher doses.

Source: Reuters; April 1, 2015.

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