Ebola Response Includes Testing Vaccines and Treatments

Jul 21, 2019

A health worker vaccinates a man who has been in contact with an Ebola affected person in the Democratic Republic of Congo in January, 2019.
Credit World Bank / Vincent Tremeau / CC BY-NC-ND 2.0, http://bit.ly/2SoMmYa

The World Health Organization has declared the ongoing Ebola outbreak in the Democratic Republic of Congo a global health emergency. Over the past year, more than 2,500 people have been infected and close to 1,700 have died. It is the second deadliest Ebola outbreak ever.

But the leader of the World Health Organization, Tedros Adhanom Ghebreyesus, says the fact that the outbreak hasn’t been even worse is a testament to both health workers and biomedical researchers. Efforts to develop vaccines and treatments for Ebola were fast-tracked after the 2014-2016 outbreak in West Africa, and multiple vaccines and treatments are now being used in Democratic Republic of Congo.

That doesn’t mean they’ve been fully approved by the FDA. Instead, their use is part of clinical trials.

Vaccines in Use

More than 160,000 people have received a vaccine that is considered safe and likely effective. Workers aren’t vaccinating everyone, but using a ring vaccination strategy modeled after what was done to contain small pox decades ago.

“Instead of vaccinating the entire population, you identify someone who is infected and you vaccinate the contacts of that person and the contacts of those contacts,” explained Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. “You essentially put a metaphorical ring around the index case.”

This strategy has limitations. As a clinical trial, it doesn’t provide the hard and fast proof of effectiveness that would lead to immediate FDA approval. For that, Fauci said, you need a randomized, controlled trial. But that’s not feasible or ethical during an outbreak.

In addition, the incubation period between exposure to Ebola and symptoms is typically about three weeks, and it takes almost two weeks for the vaccine to take effect. So, health workers are in a race to stop the spread of the virus.

“That's exactly why there's a lot of tension, and a lot of important work going on to try and keep up,” said Fauci.

But Fauci says they’ve seen a worrisome trend during this outbreak. A large fraction – sometimes more than half – of new Ebola patients were not identified among the contacts of previous patients.

“These are individuals who've gotten infected, but you really don't know what the source of infection is,” Fauci said. “That's troublesome, because that means we don't have our arms around the outbreak the way you wish you would.”

Testing New Treatments

In past outbreaks, infected patients received supportive care, but there weren’t medications to specifically fight the infection. Now, four treatments are being tested.

Most of the medications being treated are antibodies; they essentially shortcut the two weeks that it takes the body to mount an immune response and produce its own antibodies after vaccination.

Here, again, the structure of the trial is unusual. Rather than testing the four treatments against a “no treatment” control, three of the treatments are being compared to a fourth – Zmapp - that was previously found safe and likely effective. Researchers are hoping to try the treatments on 545 patients.

“We're close to that full accrual now,” Fauci said. “So, hopefully within a reasonable period of time we'll be able to take a look at the data and see if in fact there is greater efficacy in one versus another.

Fauci says they’ve already learned some important lessons that could be applied to future disease outbreaks – Ebola or otherwise.

“One of the things that we've learned from the West Africa outbreak of Ebola, and now the DRC outbreak, is that you can do ethically sound and scientifically sound clinical research within the setting of an ongoing outbreak,” said Fauci. “We have really learned a lot, and hopefully with the therapeutic trial we'll learn even more.”

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