BREAKTHROUGH: Ebola Vaccine Shows ‘Promising Results’ In Africa

An experimental vaccine that could be a first line defense against Ebola is showing promise against the deadly disease, scientists reported this week.

Results from a Phase 1 clinical trial conducted in Africa found that the vaccine, called RV 247, is safe and prompts an effective immune response in patients. However, more research is needed to see if it still offers protection months down the line, the authors report in The Lancet medical journal.

“This is the first study to show comparable safety and immune response of an experimental Ebola vaccine in an African population,” the study’s lead author, Dr. Julie Ledgerwood, said in a statement. “This is particularly encouraging because those at greatest risk of Ebola live primarily in Africa and diminished vaccine protection in African populations has been seen for other diseases.”

The vaccine, developed by the US National Institute of Allergy and Infectious Diseases (NIAID), has been in the works for years; the African trial began in 2009 in Uganda, well before West Africa’s current Ebola outbreak. It’s designed to protect against the Ebola and Marburg viruses, both of which belong to a family of viruses called Filoviridae, or filoviruses, which are known to cause severe hemorrhagic fever in both humans and nonprimates. There are five species of Ebola virus; the Zaire strain is behind the 2014 outbreak. In contrast, Marburg is a single-strain virus.

More research needed to determine duration of immune response

The vaccine trial, conducted in Kampala, Uganda, involved 108 healthy people aged 15 to 50. Between November 2009 and April 2010, researchers split the participants into four groups: 30 people received the Ebola vaccine, 30 received the Marburg vaccine, 30 got both vaccines, and 18 were given a placebo. Each participant received three rounds of injections four weeks apart.

Four weeks after the final injection, 17 of 30 people who got the Ebola vaccine showed an antibody response, meaning they developed antibodies in the blood that would help them fight off infection. Of those who received both the Ebola and Marburg viruses, 14 out of 30 showed an immune response. However, the results were not long-lasting, and the antibodies were not detectable 11 months after the last vaccine.

Safety trials showed both vaccines were well tolerated. The Marburg vaccine gave one study participant a low white blood cell count, but this was the only adverse side effect noted in the study.

The RV 247 vaccine is similar to another vaccine, known as VRC207, which was also found to be effective in an early clinical trial on humans. In November, results of the Phase 1 clinical trial of VRC207 were published in the New England Journal of Medicine, and showed the drug elicited an immune response to Ebola in 100 percent of the study participants. The researchers developing that vaccine say they will complete the trial by the end of the month in order to expedite the approval process with the U.S. Food and Drug Administration.

Key questions about vaccine remain

In a commentary on the Uganda trial findings that appears in the same Lancet issue, Saranya Sridhar, MBBS, DPhil, with the Jenner Institute at the University of Oxford in the United Kingdom, wrote that West Africa’s Ebola epidemic is a sobering reminder of the devastating effects of filovirus outbreaks.

He said a crucial question, as with other vaccines, is whether they are as safe and immunogenic (i.e., whether or not they can produce an immune response) when used in Africa as elsewhere. The Ugandan trial sheds some light on the issue, he said, yielding results similar to those of an American trial of the same vaccines and providing a glimpse of what might be expected from ongoing trials of virus-vectored Ebola vaccines in Africa.

However, Sridhar urged cautious interpretation of the results, given the small number of people in the Ugandan trial and results from tuberculosis vaccine trials that showed lower vaccine immunogenicity in African populations. He also said the low proportion of Ugandan participants who showed an immune response to the Ebola vaccine alone or combined with the Marburg virus vaccine raises the question of whether a low response to the ChAd3would affect vaccination strategies for use in West Africa’s outbreak. “Will it be necessary to give higher doses, multiple doses, or a modified vaccinia Ankara booster?” he wrote.

Sridhar said that in light of the Ebola epidemic, researchers and policymakers should ask themselves if a filovirus vaccine should have been further along in development. He added that the response shows how quickly vaccine developments can progress: “This study is the first step on the aspirational road towards the deployment of filovirus vaccines in Africa and must serve to shake the metaphorical cobwebs that can stall our advance towards this destination.