China is highly concerned about the monitoring of the mutation of COVID-19 and will optimize its epidemic control policies accordingly, said a Chinese health official on Thursday. China's National Health Commission on Monday publicized a plan to downgrade the management of COVID-19  from a Class-A to a Class-B infectious disease. Liang Wannian, head of the COVID-19 response expert panel under China's National Health Commission, said at a press conference that China is keeping a close eye on the possible mutation of the virus.