But Chinese officials and Sinopharm, the state-owned maker of the vaccine, were silent on Wednesday on the Emirati disclosures. And scientists noted that the announcement was lacking in data and other critical details.

The news that a Chinese vaccine is 86 percent effective — exceeding the 50 percent threshold set by many governments — is a boost to China’s biomedical ambitions. But it falls short of the performance reported by the American drug makers Pfizer and Moderna, which said earlier that their vaccines were more than 90 percent effective at protecting against the coronavirus…

The news release from the Emirati government provided few other key details, such as the number of Covid-19 cases that were analyzed or the ages of the volunteers, making it unclear to scientists how Sinopharm came to its conclusions.

“The devil is in the details,” said Beate Kampmann, director of the Vaccine Center at the London School of Hygiene and Tropical Medicine. “It’s very difficult to judge this without seeing the number of cases. The main thing is, the trial results need to be made public.”