Though the most recent Ebola outbreaks have been relatively small compared with the 2014-2016 epidemic, enthusiasm from biopharmaceutical companies, global agencies and other international partners has not waned in the pursuit for an effective vaccine against the virus, the U.S. government's top infectious disease expert said.
There has been "no lessening of a commitment on anyone's part," Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, or NIAID, told S&P Global Market Intelligence. "We feel this is an important public health threat."
Fauci noted that experimental vaccines from Merck & Co. Inc., GlaxoSmithKline PLC and Johnson & Johnson are currently being tested against Ebola. The Health Ministry of the Russian Federation also is among those testing a vaccine.
"I believe we are on a pathway to getting an Ebola vaccine," Fauci said, adding that research and development remains strong.
He noted that the NIAID, which is part of the National Institutes of Health, or NIH, had taken on the challenge to discover and develop an Ebola vaccine long before the outbreaks erupted in recent years.
Funding
Fauci said the NIH also has enough funding to complete its ongoing Ebola vaccine trials.
"Ebola is a high priority, so we are going to do these studies regardless of what happens with the budget," he said. Fauci said the Ebola vaccine study funds are independent of any other funding and the money is secure.
In May, President Donald Trump called on Congress to rescind the remaining $252 million from the U.S. 2015 Ebola response funds as part of his $15.4 billion rescission edict, but the administration withdrew that request a month later.
Deadly disease
Ebola is a highly contagious disease often fatal in humans, killing from 25% to 90% of those infected. The disease was first detected in 1976 in two simultaneous outbreaks in Africa — one in what is now Nzara, South Sudan and the other in Yambuku, Democratic Republic of Congo, or DRC, near the Ebola River, from which the virus takes its name.
The virus is transmitted by direct contact with the blood, body fluids and tissues of infected people or animals, such as chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines.
The 2014-2016 epidemic in the West African nations of Guinea, Liberia and Sierra Leone, in which 28,616 people were infected and 11,310 died, was the longest and most deadly outbreak of the virus recorded in global history, according to the World Health Organization, or WHO.
In the most recent outbreak in the DRC, 52 cases of Ebola have been reported — 25 laboratory-confirmed and 27 probable — with 39 of those people dying, Peter Salama, WHO's deputy director-general for emergency preparedness and response, said in an Aug. 12 tweet. He said there also were 48 suspected cases under investigation.
Merck experimental vaccine in use
Vaccinations with Merck's rVSV-ZEBOV Ebola vaccine started earlier this month in the DRC's North Kivu province in high-risk populations, such as healthcare workers in contact with infected people.
A total of 3,220 doses of the vaccine were available in the country, while supplementary doses have been requested, WHO said in an Aug. 8 statement.
The outbreak, however, has struck a densely populated active conflict zone, creating a challenge for health teams to go deep into communities to actively find cases and monitor them, WHO stated on Aug. 12.
"WHO is calling for free and secure access by all responders to the affected populations," said Tedros Adhanom Ghebreyesus, the global agency's director-general.
Just last month, WHO had declared an end to an Ebola outbreak in another part of the DRC, which started May 8. In that outbreak, 54 people were infected, with 33 dying. Merck also had provided its experimental vaccine for that outbreak.
Fauci noted that the safety and efficacy data from the people vaccinated during the two latest DRC outbreaks are being collected and will be examined by researchers.
Clinical trials
In an Aug. 10 "Viewpoint" article published in peer-reviewed medical journal The Lancet, Fauci's colleague at the NIH, Cliff Lane, deputy director for clinical research and special projects at the NIAID, and his co-authors noted that Merck's vaccine was given to children as young as one year old during the DRC outbreak that ended in July.
"It is essential that these vaccines are assessed in children," wrote the authors, who are part of an international consortium known as PREVAC.
The PREVAC team is currently conducting a phase 2 trial in Guinea, Liberia, Sierra Leone and Mali to evaluate three Ebola vaccination strategies in people one year or older.
They noted that 36 trials of experimental Ebola vaccines have been completed, while 14 are active.
So far, Merck's vaccine has shown the most promise, demonstrating 100% efficacy in an open-label, cluster-randomized trial in Guinea, though there is some debate over the data, the PREVAC team acknowledged.
In addition to more data in children, they said more data is also needed in pregnant women and people whose immune systems are compromised, like those with HIV or the elderly.
They noted that pregnant women continued to be excluded from vaccination strategies during the latest DRC outbreaks.
In addition, they said more research was needed on the durability and rapidity of immune responses generated by various vaccine approaches.
The authors also called for studies to identify reliable correlates of protection — the specific and measurable part of an immune response that would indicate a person is protected from Ebola — as well as large-scale trials to fully evaluate the safety and efficacy of experimental vaccines.
"It is important to investigate different scenarios for vaccination strategies and different vaccines to respond more effectively to future outbreaks," the PREVAC team members concluded.
Several experimental products to treat Ebola also are being investigated, with some used in the most recent DRC outbreaks, including one developed by the NIH.