In a rare admission of the weakness of Chinese Coronavirus vaccines, the country’s top disease control official says their effectiveness is low and the government is considering mixing them to get a boost. Chinese vaccines “don’t have very high protection rates,” said the director of the China Centers for Disease Control, Gao Fu, at a conference on Saturday in the southwestern city of Chengdu.

Beijing has distributed hundreds of millions of doses abroad while trying to promote doubt about the effectiveness of the Pfizer-BioNTech vaccine made using the previously experimental messenger RNA, or mRNA, process.