Can an Experimental Ebola Vaccine Put a Stop to the Latest Outbreak?

Over 4,000 doses of the vaccine have arrived in the Democratic Republic of the Congo

Ebola containmnent
A health care worker wears virus protective gear at a treatment center in Bikoro, Democratic Republic of Congo, the epicenter of the latest outbreak. Associated Press

An Ebola outbreak is currently underway in the Democratic Republic of the Congo. Health officials have identified 42 suspected, probable and confirmed cases, and 23 people have died. The disease has spread from the remote rural region where it began to Mbandaka, a city of nearly 1.2 million people, prompting fears that it will become hard to control. But a new vaccine may be able to stop the outbreak in its tracks.

As Julia Belluz reports for Vox, more than 4,000 doses of an experimental Ebola vaccine have arrived in the DRC, with another 4,000 expected to arrive in the coming days. The vaccine, known as rVSV-ZEBOV, was first created in the early 2000s, but this marks the first time that it has been used to control a new outbreak.

There are five species of Ebola; rVSV-ZEBOV protects against a strain known as Zaire, which is the one that most commonly infects humans. As Megan Jula explains in Mother Jones, the vaccine works by “trick[ing] the body into thinking it has been infected with Ebola and launching an immune response.”

Clinical trials suggest that the vaccine works very well. When it was first developed by the Public Health Agency of Canada in 2003, rVSV-ZEBOV was shown to be 100 percent effective in monkeys. But there was little interest from the pharmaceutical industry until a major Ebola outbreak in West Africa killed more than 11,000 people between 2014 and 2016. The pharmaceutical company Merck bought the rights to the vaccine in 2014.

According to Nurith Aizenman of NPR, rVSV-ZEBOV was first tested on humans in 2015, when around 7,500 people in West Africa were innoculated. Researchers used what is known as a “ring vaccination”; when a person became infected, their contacts—family, friends, neighbors—were all vaccinated, and then those individuals’ contacts were vaccinated as well.

In the past, Ebola has been controlled by isolating the sick before they can infect anyone else, but this method has not proven particularly successful at stopping Ebola’s spread through large cities. The ring vaccination method, on the other hand, was highly effective. The results of the clinical trial showed that not a single person who received the rVSV-ZEBOV went on to contract Ebola. And even when some members of an infected person’s “ring” were not vaccinated, overall transmission was reduced by about 75 percent.

“That is a big deal,” Ira Longini, a biostatistician at the University of Florida who was involved in the trial, tells Aizenman, “It's very unusual.”

The vaccine is not yet licensed, but the government of the DRC has formally asked that it be deployed under “compassionate use” protocol, which describes the use of a medical product that is still being investigated. Health officials will monitor patients for 84 days after vaccination, according to the World Health Organization (WHO). Tom Geisbert, one of the lead researchers who developed rVSV-ZEBOV, tells Jula of Mother Jones that some patients have reported “little muscle aches and pains” after receiving the vaccine. But, he added, “I would rather have a headache than Ebola.”

Administering the vaccine in Bikoro, the remote epicenter of the latest outbreak, won’t be easy. The vaccine must be kept in an environment between minus 76 and minus 112 degrees Fahrenheit, which is hard to do in a region where there is no electricity, Peter Salama, the WHO deputy director general of emergency preparedness and response, tells Jula.

But if rVSV-ZEBOV proves safe and effective, it could change the way that health officials respond to Ebola—and ensure that the disease never again reaches epidemic proportions.

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