The vaccine, based on the recombinant vesicular stomatitis virus (rVSV) platform, has been identified by experts at the World Health Organization (WHO) as the "most promising" candidate currently under development for the Bundibugyo strain—an Ebola variant for which no approved vaccine or treatment currently exists.
The announcement was made on Thursday by Hilleman Laboratories, a Singapore-based organisation that is leading the development of the vaccine amid one of the deadliest Ebola outbreaks in recent history. The epidemic has already claimed nearly 1,500 lives in the Democratic Republic of Congo, where conflict and insecurity have complicated response efforts.
Hilleman Laboratories said it is accelerating work on the vaccine to enable it to enter human clinical trials as quickly as possible.
"We’re racing to develop a Bundibugyo vaccine and make doses for clinical trials," Hilleman Laboratories Chief Executive Officer Raman Rao said in a statement.
The organisation is a joint venture between US pharmaceutical giant MSD—known as Merck in North America—and the UK-based Wellcome Trust. According to the joint statement, MSD, which developed the licensed Ebola vaccine Ervebo, "will serve as a technical adviser" by providing "expertise on the rVSV platform."
The vaccine has attracted support from the Coalition for Epidemic Preparedness Innovations (CEPI), which is providing funding for the project alongside several other Ebola vaccine initiatives. If clinical trials prove successful and regulatory approval is secured, CEPI and Hilleman Laboratories said they intend to "ensure rapid, affordable supply of doses in outbreak-affected countries and low- and middle-income settings."
Health experts consider the rVSV platform particularly promising because it has already been successfully used in Ervebo, the world's only officially licensed Ebola vaccine. However, Ervebo protects against the Zaire strain of the virus rather than the Bundibugyo strain currently driving infections in parts of Central Africa.
One of the major advantages of the new vaccine candidate is its potential for easier storage and distribution. While Ervebo requires ultra-low temperature storage, researchers hope the Bundibugyo vaccine will remain stable for several months in standard refrigeration, making it far easier and less expensive to transport to remote communities where outbreaks often occur.
WHO experts had indicated in May that it would likely take between seven and nine months before the rVSV vaccine could reach the clinical trial stage. Thursday's announcement signals continued progress toward that goal.
The vaccine works by using a modified version of the vesicular stomatitis virus—an animal virus—as a delivery system to introduce a Bundibugyo Ebola protein into the human immune system. This prompts the body to produce an immune response without causing Ebola infection.
The latest development comes just one week after researchers at Oxford University administered the first dose of another experimental Bundibugyo Ebola vaccine to a volunteer in a rapidly launched clinical trial, highlighting the growing global effort to find effective protection against the rare strain.
The current Ebola epidemic in the Democratic Republic of Congo has become the third-largest outbreak ever recorded. Since May, health authorities have confirmed 3,360 infections, including 1,487 deaths, with the northeastern province of Ituri remaining the epicentre of the crisis.
The outbreak has also spread beyond DR Congo's borders. In neighbouring Uganda, health officials have confirmed 20 cases, including two deaths, raising concerns about wider regional transmission.
Ebola is a severe viral haemorrhagic fever that spreads through close contact with infected individuals or exposure to contaminated bodily fluids. The disease can cause fever, vomiting, severe bleeding and organ failure, and remains one of the world's most lethal infectious diseases when outbreaks are not rapidly contained.