In a desperate gamble against the fastest-growing Ebola outbreak in history, health officials in the Democratic Republic of Congo are injecting frontline workers with a vaccine designed for a different disease. This isn’t a cure—it’s a Hail Mary pass played with human lives. The rollout began Saturday in Bunia, the crumbling epicenter of Ituri province, where the Bundibugyo virus has already claimed at least 3,639 souls and infected over 7,500, with bodies piling up faster than hope.

The weapon of choice? Ervebo, a vaccine approved for the Zaire strain of Ebola. Against the current nightmare strain, its effectiveness is a terrifying question mark. ‘We don’t know to what degree it might be effective,’ admitted Steve Ahuka, a member of the health task force, in a chilling understatement. Some 50,000 doctors, nurses, and burial workers—the brave souls marching toward the epicenter—will receive the shot under a ‘compassionate-use’ program, a bureaucratic term meaning ‘we have nothing else.’

Of those, 20,000 will become unwitting subjects in a year-long clinical trial, their survival data the only currency in this bleak experiment. At a health facility in Bunia, Dr. Jeannot Elua summed up the grim resignation: ‘We healthcare workers don’t really have a choice. We are going to receive it.’ He’d already taken a mandatory, different vaccine in a previous outbreak. This is the life on the frontlines: a perpetual lottery of experimental jabs.

The operation, backed by the World Health Organization and Doctors Without Borders, is a race against a predator that shows no sign of slowing. While WHO officials cling to ’encouraging signs,’ MSF delivered a brutal reality check Friday, warning there is ’no clear evidence the epidemic is coming under control.’ The math is horrifyingly simple: no licensed vaccine exists, no proven treatment is available, and the world’s medical arsenal is firing blanks.

As the first doses enter arms in North Kivu, where cases are soaring, the scene is one of profound courage shadowed by profound uncertainty. These health workers, already ‘particularly exposed,’ are now human subjects in a global trial by fire. The world watches, sends thoughts, and prays the mysterious jab works—because if it doesn’t, the body count will tell a story science wasn’t ready to hear.