Merck’s Ebola Vaccine Helps Combat Deadly Outbreak in the Congo as the Virus Spreads
The latest outbreak has helped fast-track limited governmental approval for some experimental vaccines that didn’t exist just a few years ago
What to Know
- The ongoing Ebola outbreak in the Congo is the second-deadliest on record, killing an estimated 1,625 people
- Health-care workers were granted approval to use an unlicensed vaccine made by Merck & Co.
- WHO data shows the Merck vaccine had a 97.5% efficacy rate for those who were immunized compared to those who were not
The Ebola virus is once again wreaking havoc in the war-torn North Kivu and Ituri provinces of the Democratic Republic of the Congo, claiming an estimated 1,625 lives so far in its second-deadliest outbreak ever.
The ongoing outbreak follows the most devastating Ebola epidemic in history, which killed 11,310 and infected 28,616 people in Guinea, Sierra Leone and Liberia in West Africa from 2014 to 2016.
However, the latest outbreak, which has infected more than 2,400 people in the DRC since August, has helped fast-track limited governmental approval for some experimental vaccines that didn’t exist just a few years ago.
The disease first appeared in Africa in 1976. It’s transmitted from animals to humans and is highly contagious among the human population from there — through direct contact, contamination of objects or even contact with the dead. Ebola hemorrhagic fever, as it’s known, “is a rare but severe, often fatal illness in humans” that kills about half of all people who become infected with the virus, according to the World Health Organization.
And it’s been ravaging the Congo in recent months.
Just a week after the DRC declared the Ebola outbreak in August, health-care workers were granted approval to use an unlicensed vaccine made by New Jersey-based Merck & Co. on a “compassionate basis,” which allows the use of an unapproved drug when no other options are available. It’s the first time the vaccine, which was still undergoing clinical trials during the West African outbreak earlier this decade, is being widely used and is being hailed as a “savior” for health-care workers in the Congo.
Dr. Mike Ryan, executive director of the WHO’s health emergencies program, said the experimental vaccines have been critical to the response mission in the DRC.
“One of the biggest saviors for us in this response, in my view, has been our ability to use vaccine very tactically in vaccinating around cases, contacts, contacts of contacts and we believe that has reduced transmission significantly,” Ryan told reporters in Geneva, Switzerland, in May. “Every time we fall behind in that process of vaccination the virus intensifies in its transmission.”
Merck’s Ebola vaccine, called rVSV-ZEBOV, was still undergoing clinical trials during the West African outbreak earlier this decade, when it was used to immunize about 16,000 volunteers as part of a clinical trial. Merck donated the experimental vaccine, which showed early promise in combating the virus, to the World Health Organization again during a smaller Ebola outbreak in the DRC in 2018.
This time, it’s being used on a much wider scale.
Dr. Beth-Ann Coller, who leads Merck’s Ebola vaccine clinical development program, said more than 135,000 people have received the vaccine in the current outbreak in the Congo.
WHO data shows the Merck vaccine had a 97.5% efficacy rate for those who were immunized compared to those who were not. Despite this, the organization said more research needs to be done before it can be officially licensed. The experimental vaccines have proven highly effective in combating the Zaire strain of the Ebola virus, according to the WHO, and have helped health-care workers in their effort to stop the spread of Ebola. However, major barriers continue to stand in their way.
The vaccine is not yet licensed by any government agencies. However, Coller said the company has submitted licensing filings in both the U.S. and E.U. The Food and Drug Administration is currently assessing Merck’s application. Coller added that the WHO and a number of at-risk African countries are also helping to review the vaccine.
“There’s a tremendous parallel effort ongoing to review the dossier and to attempt to achieve licensure as quickly as possible, particularly for the African countries that are at risk,” Coller said.
The vaccine is being deployed using a so-called ring strategy so that people who come in contact with infected people, as well as the contacts of those contacts, are immunized. Health workers and other aide workers are also given the vaccine.
The WHO ramped up its prevention efforts in early May, allowing more people to receive the Merck vaccine. Another experimental vaccine developed by Johnson & Johnson may also soon be cleared for use for people considered at risk of contracting the virus. Health-care workers and others who came in contact with the victims in the Uganda cases were also immunized.
Though the WHO’s strategic advisory group in May warned the organization could run out of doses of the Merck vaccine if the outbreak continues, Ryan later said there are about 250,000 doses ready to ship and an additional 100,000 available by the end of the year. Merck also said it’s developing an additional 450,000 doses that will be ready in about a year.
Though the vaccines serve as a way for health workers to stem the spread of the virus, they don’t provide much value to those who have already contracted the disease, said Dr. John Dye, chief of viral immunology at the U.S. Army Medical Research Institute of Infections Diseases.
There isn’t yet a known cure for someone once they are infected with Ebola, which causes a high fever, hemorrhaging in some and even death. Currently, supportive care is widely implemented to treat Ebola patients.
‘Hydrate, hydrate, hydrate’
“Basically hydrate, hydrate, hydrate and survive it until your immune system catches up,” said Dr. Joe McDonough, director of pharmaceuticals and bioengineering at the Southwest Research Institute, which has been working on its own treatment for the disease. The nonprofit research group is attempting to develop small molecule inhibitors that will stop the virus from replicating and attack the pathogen, while not harming the people who are sick.
However, McDonough said the institute is “very much in the research phase” and has seen some success in attacking the virus in mice, but the treatment has been causing some toxicity in the hosts.
Ebola symptoms appear two to 21 days after contact and can mimic the flu or malaria, presenting with fever, severe headache, muscle pain, weakness, fatigue, diarrhea, vomiting and unexplained bleeding or bruising, especially in later stages.
Death comes fast
It takes about one to two weeks after infection to begin recovering from the disease. Death typically comes just as fast if a patient isn’t able to mount a defense against the virus, generally from multiple organ failure and shock.
That’s why staying hydrated is key to surviving the virus, McDonough said.
“That’s all you can really do because the clinical presentation is internal hemorrhage and horrendous loss of fluids, so if somebody can stay hydrated and the kidneys can not shut down long enough for an immune response to be mounted and successfully so, someone can survive it,” he said.
That doesn’t mean researchers aren’t working to find a cure, though.
Four potential treatments are undergoing a clinical trial coordinated by WHO to test their efficacy on those who have already been infected in the DRC. It is the first-ever multi-drug trial to find a successful treatment for Ebola. Three of those experimental treatments were also cleared for use in Uganda.
Searching for a cure
One of those treatments, Mapp Biopharmaceutical’s ZMapp, “provided the highest quality evidence available to date for efficacy for an Ebola therapy, though did not reach target enrollment,” a panel of experts convened by the WHO said in August.
According to WHO spokesman Christian Lindmeier, more than 1,000 people in the DRC have been treated with one of the four of the experimental therapies under a regulatory framework called Monitored Emergency Use of Unregistered Interventions, or MEURI, which allows the use of experimental treatments for patients outside of clinical trials under certain circumstances.
Lindmeier said more than 370 of those who had been treated had also consented to enrollment in a clinical trial that has been ongoing since November. The experimental treatments include Mapp Biopharmaceutical’s ZMapp, Regeneron Pharmaceuticals’ REGN-EB3 and Gilead Science’s Remdesivir and mAb114, which is licensed to Ridgeback Biotherapeutics.
WHO said it cannot share more details of the results until the clinical trial is complete.
Spread beyond Africa
WHO officials said the current outbreak shouldn’t worry international officials. However, there’s always a risk of the virus spreading beyond the Congo’s borders, said Dye, the Army’s chief of viral immunology. That’s especially true in a country like the DRC, which doesn’t have tight borders like in the U.S. and has been entrenched in violent political conflict for decades.
That violence has had a major impact on the Ebola containment effort with more than 130 attacks on health-care facilities between January and mid-May, according to the European Commission. WHO said local populations mistrust health-care workers, and it’s facing a $54 million funding gap for its Ebola response, making matters worse.
Though the CDC says the risk of global spread of the virus remains low, Dye noted that the West African outbreak earlier this decade devastated three countries and even spread to the U.S.
Liberian national Thomas Eric Duncan died in a Dallas, Texas hospital in 2014 after travelling from Liberia during the outbreak, prompting five U.S. airports to screen for the fever.
“As interconnected as we are, it is not unheard of, nor unprecedented, for the virus to come to countries you would not consider local to the African nations where this is occurring,” Dye said. “As globalization continues ... it’s become more and more likely — to the point where we really don’t have a ‘my backyard, your backyard’ situation. It’s everybody’s one giant backyard of the world.”
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