Fever was the first sign of trouble in a group of macaques, but those vaccinated with the rVSV Bundibugyo vaccine showed no symptoms. Yet despite its promise, the vaccine has remained unused for years due to lack of funding and interest.

Thomas Geisbert, an immunology professor at the University of Texas Medical Branch in Galveston, developed this vaccine after his initial breakthrough in 2003. However, commercial interest was low due to the limited market for an ebola vaccine.

The current outbreak in Central and East Africa has caused over 200 deaths, yet Geisbert’s vaccine remains untested on humans. The World Health Organization has identified it as one of the most promising candidates, given its success against different strains of the virus.

With the Bundibugyo strain now causing widespread suffering, there's a critical need to test and deploy this vaccine. In 2013-2016, a similar rVSV-based vaccine by Merck was deployed successfully in West Africa, offering hope for rapid progress with Geisbert’s candidate.