Since it was discovered in 2012, the camel-borne virus causing Middle East respiratory syndrome (MERS) has sickened more than 1200 people in the Middle East and killed more than 500 of them. Scientists worry that the slow-burning epidemic could turn into a global pandemic if the virus changes, so they’re hard at work on candidate vaccines for people. But to stamp out the virus before it escalates into an emergency, says Christian Drosten, a virologist at the University of Bonn in Germany, “the best strategy is trying to suppress circulation of the virus in camels.” This week online in Science a team reports encouraging results for one candidate camel vaccine, though its main effect—reducing the level of virus shed by the animals—may not be enough to stop MERS’s circulation. Nor is it clear whether the vaccine gives lasting protection or whether camel owners will accept vaccinating against a disease that causes hardly any symptoms in the animals.