DRC is no stranger to Ebola outbreaks. Why isn’t there a vaccine or treatment to help now?

The Democratic Republic of Congo (DRC) is battling its 17th Ebola outbreak since the virus was discovered there in 1976, with the current outbreak caused by the less-common Bundibugyo strain. This outbreak, now the third-largest on record, has raised global concern due to the lack of an approved vaccine or treatment specifically for this strain. The Bundibugyo strain has caused smaller outbreaks before, including one in 2012 with 38 confirmed cases and 13 deaths, and another in 2007 with 131 cases and 42 deaths. In contrast, the Zaire strain, responsible for the deadly 2014-2016 West Africa outbreak and a 2018-2020 DRC outbreak, has killed over 11,000 and 3,000 people respectively. A vaccine for the Zaire strain, Ervebo, was developed during the West Africa outbreak and approved by the FDA in 2019. Experts are considering whether Ervebo could offer limited protection against Bundibugyo, but evidence is scarce. A 2011 study involving four monkeys showed partial protection, but larger trials are needed. WHO’s chief scientist, Dr. Sylvie Briand, stated that Ervebo is not a top choice due to insufficient cross-protection data. Safety risks also exist, as diverting the immune system toward Zaire Ebola could worsen a Bundibugyo infection. Merck, the manufacturer of Ervebo, has supplied over 500,000 doses to a global vaccine stockpile but emphasizes the need for further research. The World Health Organization (WHO) representative in the DRC, Dr. Anne Ancia, acknowledged the uncertainty in using the vaccine, while experts like Dr. Thomas Geisbert of the University of Texas Medical Branch warn that the limited data suggests only around 50% protection at best. The ethical and logistical challenges of deploying an untested vaccine in this context remain significant.