The decision is a crucial step in getting shots to the Democratic Republic of Congo, the center of the outbreak.
The World Health Organization has given its authorization to a first vaccine to protect against mpox, a decision announced in such haste on Friday that it caught even the head of the company that makes the vaccine by surprise.
The vaccine, made by the Danish company Bavarian Nordic, has been approved by the regulatory authorities in Europe as well as the United States and other high-income countries since a global mpox outbreak in 2022. But low- and middle-income countries rely on the W.H.O., through a process called prequalification, to determine which drugs, vaccines and health technologies are safe and efficient uses of limited health funding, and the organization had declined to act until now.
The W.H.O. had come under increasing criticism for declaring a global public health emergency for mpox last month without giving a vaccine that prequalification stamp of approval, or a more provisional form of approval called emergency use authorization. Bavarian Nordic first submitted its safety and effectiveness data on the vaccine, called Jynneos, to the W.H.O. in 2023. The W.H.O. had defended its slow pace of review, saying that it needed to subject the vaccine to careful study because it, and two others that have been used to protect against mpox, were originally designed as smallpox immunizations, and because delivering it in low-resource settings such as Central Africa would involve factors different from those relating to its use in high-income countries.
But on Friday morning, the W.H.O. suddenly said it was authorizing the shot.
“This first prequalification of a vaccine against mpox is an important step in our fight against the disease, both in the context of the current outbreaks in Africa, and in future,” Dr. Tedros Adhanom Ghebreyesus, the W.H.O. director general, said in a statement.
Paul Chaplin, Bavarian Nordic’s chief executive, said he was among the many who had been caught off guard.
“We’ve got there eventually — I don’t know quite how,” he said. “But it’s good news. It’s going to make the regulatory pathway much easier.”