The current Ebola outbreak in central Africa has prompted the World Health Organization (WHO) to raise its highest level of concern, with experts warning that there is neither an approved vaccine nor specific treatment for the Bundibugyo virus now circulating.
The situation is the result of failures stretching back years.
According to health experts, there are currently three main Ebola vaccines.
The problem is that all of them target the so-called Ebola virus (EBOV) – formerly known as Zaire ebolavirus – within the Ebola virus genus.
Further vaccines, e.g. against the Sudan Ebola virus (SUDV), “are currently at various stages of development and are, in some cases, being used in clinical trials”, according to the German health body Robert Koch Institute.
Two further Ebola strains known to be dangerous to humans exist beyond the two already mentioned: Tai Forest and the pathogen behind the current outbreak, Bundibugyo (BDBV).
Are there Bundibugyo vaccines?
All vaccines against the Bundibugyo virus are still at the pre-clinical stage, says Bernhard Nocht Institute for Tropical Medicine Virus Immunology Research Group head Prof Dr Cesar Munoz-Fontela in Hamburg, Germany.
That means none have yet been tested in humans – not even, as is usually the first step, for safety in a smaller Phase 1 clinical trial.
That’s not all: There is also no stockpile of Bundibugyo vaccine doses that could now be tested for safety, and subsequently, for protective efficacy in humans.
Producing a sufficient quantity of vaccine doses would take weeks to months, even if production could begin immediately, says University Medical Centre Hamburg-Eppendorf infectious disease physician Prof Dr Marylyn Martina Addo.
After the major Ebola epidemic in West Africa in 2014 and 2015, which killed more than 11,000 people, experts had urged that vaccines against all dangerous Ebola strains be tested for safety, and then produced in sufficient quantities to be deployable in the event of an epidemic.
“Had we been able to do that 10 years ago with prioritised financial resources,” she says, “we would have been prepared now.”
“We need to produce vaccine doses and therapeutics that are at least ready for clinical trials,” stresses Prof Munoz-Fontela.
“And this strategy must be implemented before an outbreak, not after one.”
Beyond acute epidemics, however, there is little interest in such diseases, the virologist says.
How about current vaccines?
The available approved Ebola vaccines could possibly provide a little protection against the Bundibugyo virus.
This is as there is a close relationship between the Ebola virus and the Bundibugyo virus, explains University of Leipzig Institute for Drug Development vaccine design specialist Assistant Prof Dr Clara Schoeder.
Antibodies produced in response to Ebola vaccines could therefore potentially neutralise the Bundibugyo pathogen, but nobody knows how pronounced such an effect might be.
In a small study published in 2011, three of four rhesus monkeys vaccinated with a so-called rVSV-EBOV vaccine preparation survived infection, but all four fell ill.
Prof Munoz-Fontela warns against deploying Ebola vaccines whose safety is established, but whose efficacy against Bundibugyo is unclear.
If the vaccine proved to be of limited effectiveness, the hard-won trust in the vaccine that offers strong protection against the Ebola virus could be undermined in the region.
“More evidence is needed for that,” says Prof Addo.
The plan is to additionally test the efficacy of the VSV vaccine against Bundibugyo in the laboratory using serum from people vaccinated with VSV-EBOV.
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How about treatment?
Marburg University Institute of Virology Becker Lab executive director Prof Dr Stephan Becker says that there are no specific approved treatments.
“But here too there are antibodies that have protected animals against Bundibugyo, though they have not been clinically tested.”
Other experts point out that early detection and treatment in a specialised treatment centre is critical for prognosis.
“We know that mortality can be significantly reduced through good supportive therapy,” says Heinrich Heine University Hospital Tropical Medicine Unit head Prof Dr Torsten Feldt.
“This includes, for example, fluid and electrolyte management; treatment of shock, bleeding and organ dysfunction; the administration of oxygen; and the treatment of co-infections.”
What role does poverty play?
“Ebola virus outbreaks are driven by human-to-human transmission,” says Prof Munoz-Fontela.
Social factors such as refugee flows, poverty and poor living conditions therefore make it easier for the pathogen to spread following an outbreak.
Africa Centres for Disease Control and Prevention (CDC) director-general Dr Jean Kaseya adds that pharmaceutical companies see little commercial opportunity in the Bundibugyo pathogen in Africa.
“But believe me, if Bundibugyo were in Western countries, the medical countermeasures would exist.” – By Walter Willems/dpa
