Health Team

Experimental Ebola vaccine could be 'game-changer' in Congo outbreak

Health officials remain hopeful that an experimental Ebola vaccine will help control the outbreak sweeping the Democratic Republic of Congo in central Africa.

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Jacqueline Howard (CNN)
(CNN) — Health officials remain hopeful that an experimental Ebola vaccine will help control the outbreak sweeping the Democratic Republic of Congo in central Africa.

Since April 4, 45 hemorrhagic fever cases have been reported, including 25 deaths, the health ministry said Thursday. Fourteen of those cases are confirmed to be Ebola virus disease, 10 are suspected and 21 are probable.

The WHO has deployed doses of the experimental vaccine along with emergency teams and equipment Congo. There are more than 5,000 doses of vaccine in Kinshasa, the country's capital, and health officials are expecting another batch of about 4,000 doses, said James Fulker, a spokesman for the international organization Gavi: the Vaccine Alliance.

"Most of the time, Ebola is contained purely by public health measures. So this is the first time that a vaccine that has been shown to have efficacy is being employed in the control of Ebola. So in that respect it's unique," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in the United States, who oversees an extensive research portfolio that includes studies on the Ebola virus.

Between 2015 and 2016, the experimental vaccine was given to people in Guinea and Sierra Leone who were in contact with patients who had recently confirmed cases of Ebola, according to a study on that trial published in the journal The Lancet. The estimated vaccine efficacy in that study was 100%.

Now, for the vaccine, it's showtime once again -- and because the vaccine is experimental, meaning it's still being studied, it is administered with strict protocols hinging on informed consent.

How the vaccine works

The vaccine -- called rVSV-ZEBOV -- must be kept between minus 60 and minus 80 degrees Celsius (minus 76 to minus 112 degrees Fahrenheit) and are believed to last two weeks under basic refrigeration.

Cold storage in Mbandaka -- a city of nearly 1.2 million people in Equateur Province in northwestern Congo -- is in the process of being set up. The latest case of Ebola virus disease was confirmed Thursday in Wangata, one of the three health zones of Mbandaka.

There are multiple strains of the Ebola virus. For instance, the three species Zaire ebolavirus, Bundibugyo ebolavirus and Sudan ebolavirus are responsible for the larger Ebola outbreaks in Africa. This vaccine covers those in the Zaire group.

"It works by inducing in the body a response that can protect against the Ebola virus. It's usually an antibody response, namely a protein that the body induces to be able to protect against Ebola," Fauci said.

"Right now, there are still vaccine trials that are going on. Originally, the vaccine was shown to have some efficacy when it was used in a ring vaccination in Guinea, but the trials that went on in Sierra Leone and Liberia were merely to prove safety and whether or not it induced an immune response that you might predict would be protective," he said.

The vaccine, from the pharmaceutical company Merck, is used in a ring vaccinations strategy: vaccinating the close contacts of Ebola cases and the contacts of those contacts, such as family members; a buffer or "ring" of immune people around those who are sick can keep the disease from spreading.

In addition to the rings, Ebola health care workers and front line works are vaccinated, said Ira Longini, a biostatistician at the University of Florida in Gainesville, who was part of the research team leading the Ebola vaccine trials.

Anyone receiving the vaccine will then be checked three, 14, 21, 42, 63 and 84 days later.

"The estimated efficacy during the trial was 100%, and it's pretty much that simple. It protects you against illness if you're vaccinated before you're infected," Longini said.

"There's no effective treatment against Ebola. It has about a 50% death rate for those who become ill, so there's very little we can do except vaccinate, and so the vaccine is very important," he said. "In addition, the vaccine not only protects those who are vaccinated but also those around those who are vaccinated. It affects them indirectly, so it can be quite effective in stopping an outbreak or preventing the outbreak from getting large."

'This particular vaccine ... does look hopeful'

The ring vaccination strategy was used against smallpox in the 1970s, until it was officially declared eradicated in 1980.

"So the strategy's been used before, and it's been used successfully," said Dr. Daniel Lucey, a senior scholar with the O'Neill Institute for National and Global Health Law and adjunct professor of medicine-infectious disease at Georgetown Law, who is a spokesman for the Infectious Diseases Society of America.

Regarding the Ebola vaccine, "as I understand from comments from the World Health Organization and Democratic Republic of Congo this week, it will be used not surprisingly in the same way that it was first studied during the West African Ebola outbreak initially in Guinea," said Lucey, who has treated Ebola patients during outbreaks in Sierra Leone and Liberia.

"This particular vaccine, although it's still experimental, does look hopeful from past experience in Guinea and Sierra Leone, but we don't know for sure," he said. "If in fact it is safe and effective, it really will be a game-changer in terms of being able to more quickly stop future Ebola epidemics."

This vaccine isn't the only Ebola vaccine out there. There are multiple Ebola vaccine candidates in development, including the cAd3-EBOZ vaccine, which was found to be well-tolerated and induced an immune response, according to findings presented in February 2016.

Ebola virus disease, formerly known as Ebola hemorrhagic fever, is spread through direct contact with bodily fluids of a person who is sick with or has died from the disease.

"It never spreads through the air, thankfully," Lucey said.

"So the idea is to vaccinate people who come into contact or are in contact of people who come into contact with people who have Ebola virus infection," he said. "And importantly, this vaccine can never cause Ebola disease, because it contains only one small part of the Ebola virus, so it could never cause the disease itself."

West Africa experienced the largest recorded outbreak of Ebola over a two-year period beginning in March 2014. A total of 28,616 confirmed, probable and suspected cases were reported in Guinea, Liberia and Sierra Leone, with 11,310 deaths, according to the WHO.

Last week, the government of the Democratic Republic of Congo declared the current Ebola outbreak, its ninth since the discovery of the virus near the country's Ebola River in 1976.

"Right now, it is impossible to tell what's going to happen with this. Is it going to be a big outbreak? Is it going to be a medium outbreak or a small outbreak? ... We don't know at this point. That's why we're treating it as a very serious situation," Fauci said.

"I think the important takeaway message is that in the outbreak that took place in western Africa, we were able to be able to develop a vaccine and show that it works," he said. "So right now, this is a good example that you can and should be able to do research that tests the efficacy of products during an outbreak, the way it was done in West Africa."

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