WHO prioritizes two vaccines for consideration as Ebola treatments

WHO and the International Severe Acute Respiratory and Emerging Infection Consortium announced today that whole-blood therapies and convalescent serum can be used to treat Ebola.

After discussions between WHO clinicians and virologists and partners from the International Severe Acute Respiratory and Emerging Infection Consortium, two vaccines were prioritized for consideration as Ebola treatments: chimpanzee adenovirus serotype 3 (ChAd3) vaccine and recombinant vesicular stomatitis virus (rVSV) vaccine. Efficacy and safety when treating Ebola in humans has not been proven for either vaccine. However, ChAd3 has been used to treat other diseases and appears relatively safe, according to a report from WHO.

“Safety studies are currently underway in the United States of America, and are soon to start in Europe and Africa. Safety results may be available in November 2014. This would open the way for use in affected countries, initially starting with health care workers and other frontline staff, as advised by the ethics panel that met recently,” Marie-Paule Kieny, PhD, assistant director-general of WHO, said during a press conference.

Marie-Paule Kieny

Besides ChAd3 and rVSV, several other promising experimental treatments exist. They include: a convalescent plasma; a cocktail of three chimeric mouse-human monoclonal antibodies (ZMapp, Mapp Biopharmaceutical); a hyperimmune globulin prepared by purifying and concentrating plasma from immunized animals or previously infected humans; a lipid nanoparticle siRNA (TKM-100802, Tekmira); a phosphorodiamidate oligonucleotide (AVI-7537, Sarepta Therapeutics); favipiravir (T-705, Toyama Chemical/Fuji Film); an adenosine analog (BCX4430, BioCryst); and interferons.

“Several of the experimental therapies have shown promise in animal studies, while others have gone under some safety testing in humans but have not yet been proven effective against Ebola virus disease in humans,” Kieny said during the press conference. “These will now be the focus of priority clinical evaluation in affected countries, using standard protocol in order to allow determination of their efficacy as soon as possible.”

Although ZMapp has received a significant amount of attention, there is not enough experience with the treatment to conclude its efficacy or safety, according to Kieny.

“So with ZMapp, as other therapeutics, as soon as there are more supplies available, they will be evaluated in population, in treatment centers in the affected country in order for researchers and the community to definitely conclude on whether this treatment works or not,” Kieny said.

In the meantime, strategies highlighted in the recently issued WHO roadmap should be followed. Identifying patients with Ebola, isolating them and treating them has made a significant impact on the outbreak.

“We know that if we have a good standard of care, we can decrease mortality rate significantly. We need to identify the contacts, to trace the contacts, and to isolate them if they become sick,” Kieny said during the press conference.

“There is a real opportunity that a blood-derived product can be used now and can be very effective in treating patients. With the very negative point that we have so many patients, there is also the positive point that there are many people who are convalescent, who survived and are doing well, and can provide blood and serum in order to have something to treat patients now,” Kieny concluded.