WEDNESDAY, April 1, 2015 (HealthDay News) -- Researchers say preliminary tests show that people given a single shot of an experimental Ebola vaccine mounted an immune response to the vaccine.
Two separate teams of investigators concluded the vaccine is safe, with side effects confined to fever, fatigue, injection-site pain and/or joint pain.
That said, these early findings are only the first step in what will be a long road toward use in the general population. And the preliminary testing does not yet speak to the effectiveness of the vaccine in actually preventing Ebola infections.
"I would definitely say that both these efforts are moving the needle forward, because in order to get a vaccine into widespread use you have to go through several phases of studies, the first of which is designed to demonstrate overall safety," explained Dr. Amesh Adalja, a health security and infectious diseases expert with the UPMC Center for Health Security in Baltimore.
"Both teams have shown that although there are some side effects, the vaccine is basically safe," added Adalja, who was not part of either research effort. "That's an important finding in the vaccine development process. Because even though the current outbreak will eventually be completely controlled, we do want to be sure we have something safe and effective in place for the next time that an outbreak occurs."
The reports on what is known as the recombinant vesicular stomatitis virus-based vaccine (rVSV) are published online April 1 in the New England Journal of Medicine. One team was guided by corresponding study author Dr. Claire-Anne Siegrist, of the Center for Vaccinology at Geneva University Hospitals in Switzerland. The other team was led by Dr. Jason Regules, from the Walter Reed Army Institute of Research, in Silver Springs, Md.
Regules' team noted that since the current Ebola outbreak began in West Africa in December 2013, the virus has claimed the lives of just over 10,000 patients, out of slightly more than 25,000 confirmed cases.
In Regules' case, he and his colleagues conducted two phase 1 trials (funded in part by the U.S. National Institutes of Health), involving just 52 participants who were broken down into groups of 13.
In each group, three participants were injected once with a dummy vaccine, while 10 received either a low dose or high dose of the new rVSV vaccine.
By the end of a 28-day study period, the team found that those who got the vaccine had safely developed an immune responses, with more antibodies generated among the high-dose participants.
Similarly, Siegrist and his colleagues conducted three phase 1 trials, involving a total of 158 participants located in both Europe and Africa.
All the participants were injected with the same rVSV vaccine, but at different doses.
Roughly a third of the patients developed a short-lived fever, while about a fifth developed joint arthritis. Antibody responses were observed in all vaccine groups.
Both teams concluded that the results call for more testing of the vaccine.
Dr. Ronald Waldman, a professor of global health with the Milken Institute School of Public Health at George Washington University in Washington, D.C., said that will mean an exponentially larger effort to determine whether the rVSV vaccine is effective.
"There are six or seven preventative vaccines in the pipeline at the moment, all of which have promise," Waldman noted. "The rVSV vaccine contains bits of genetic material taken from the Zaire Ebola [the one circulating in the current outbreak] and inserted into another virus, which means that there is no chance that anyone will get Ebola from this vaccine.
"But the purpose of phase 1 trials is just to make sure that a vaccine is safe at the crudest level," explained Waldman. "The next step will involve anywhere from 200 to 2,000 people, and will try to identify how much is needed to get a safe immune response. After that will be a big jump to tens of thousands of people, and that's where we'll see if the vaccine actually protects against the disease. It's one thing to say a vaccine produces antibodies. It's another to say that a person who is vaccinated will not get the disease."
Waldman lamented the late-breaking nature of the effort, given that there have already been 21 other outbreaks since Ebola first surfaced in 1976. "Until now, there just wasn't sufficient degree of interest in funding the research," he said.
"But I will say that this time there's been a remarkable and unprecedented cooperation and collaboration between the public and private sector, between the CDC [U.S. Centers for Disease Control and Prevention] and the NIH [U.S. National Institutes of Health], and between drug companies," Waldman added. "Everyone's working together now, with one goal in mind -- to develop a preventative or curative product that works. And that's good news."
More information
There's more on the current Ebola outbreak at the U.S. Centers for Disease Control and Prevention.
