Cluster bombing

THE outbreak of Ebola fever in Guinea, Liberia and Sierra Leone, which has killed more than 11,000 people, has dropped out of the news as it has been brought under control. Although new cases are now measured in dozens, rather than hundreds, a week, the disease has not been stamped out—and a new epidemic could flare up somewhere else at any time. A vaccine against the virus responsible would be of enormous value. And a paper in the Lancet suggests one is now available.

The vaccine, developed by the Public Health Agency of Canada and called rVSV-ZEBOV, smuggles one of the Ebola virus’s coat proteins into a person’s body in a Trojan horse called a vesicular stomatitis virus. This horse-and-cattle virus does not cause human illness, but its presence is enough to activate the immune system, which learns to recognise and react to the Ebola coat protein—and thus, the vaccine’s inventors hope, to clobber Ebola if it should encounter it.