A clinical trial of two experimental Ebola vaccines is expected to start in Liberia in the next couple of weeks, the National Institutes of Health said Thursday, even as the number of new cases in the three mainly affected countries in West Africa declines.
"NIH is pursuing development of vaccines and treatments that could still be of use in this current outbreak, particularly in the event of a rebound, as well as future outbreaks, which, as we all know, have shown to be inevitable," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told reporters in a conference call.
Since the outbreak began, there have been 21,759 people infected, and 8,668 people have died, according to the World Health Organization. New cases, though, have been declining in the three most-affected countries in West Africa—Liberia, Guinea and Sierra Leone—with each country now having the ability to isolate and treat patients, and enough capacity to bury everyone who died from the disease.
The trial will evaluate experimental vaccines being developed by GlaxoSmithKline and NewLink Genetics, which recently partnered with Merck. Both have received support from the NIH. It will enroll primarily people at the highest risk of contracting Ebola: health-care workers, household contacts of those infected, people tracing contacts of patients, and members of burial teams, Fauci said.
Patients will be sorted into three groups: one receiving the GSK vaccine, one the NewLink/Merck vaccine, and one placebo. Placebo-controlled studies are "considered the gold standard" to determine safety and efficacy, Fauci said.
Health-care workers are considered at particularly high-risk; more than 800 have been infected with Ebola in Liberia, Guinea and Sierra Leone, and almost 500 have died. The incidence of infections among health-care workers has declined in Liberia and Sierra Leone, the WHO said Jan. 21, but rose in Guinea through December.
The trial will start by enrolling about 600 people, Fauci said, and is designed to include 27,000 in total. The Centers for Disease Control and Prevention is also pursuing a vaccine trial in Sierra Leone.
In addition to vaccines, the U.S. has been supporting development of drugs to treat Ebola patients. It has been working with the Liberian government to test the experimental Ebola drug ZMapp in a multicenter study in the U.S. and Liberia, Fauci said. That could include about 150 people, said Robin Robinson, director of the Biomedical Advanced Research and Development Authority, or BARDA.
ZMapp, a cocktail of monoclonal antibodies made in tobacco plants, was given to several Ebola patients earlier in the outbreak, though supply was quickly depleted. BARDA has been backing development of the compound, or similar compounds, both using tobacco plants and through another common drug development technique using Chinese hamster ovary, or CHO, cells. Robinson said the U.S. has been collaborating with drugmakers Regeneron and Genentech since September to pursue that strategy.
"We're taking extraordinary steps to be proactive and flexible in our response," Luciana Borio, the Food and Drug Administration's director of the Office of Counterterrorism and Emerging Threats, said on the call. "Sadly, this will not be the last Ebola outbreak, and our efforts matter for generations to come."