Unlike their Western competitors, most Chinese companies have not disclosed data from late-stage clinical trials that would show whether their vaccines are effective; just one, the state-owned Sinopharm, has released findings, which it did on Wednesday with minimal details. Regulators in China have not officially approved any of them.

That has not deterred local governments across the country, which have begun an ambitious vaccination campaign. The goal is to inoculate 50 million people — roughly the population of Colombia — by the middle of February, before the Lunar New Year holiday, when hundreds of millions of people are expected to travel.