BEIJING, Feb. 28 (Xinhua) -- China has offered plasma therapy for 245 COVID-19 patients by Friday, and 91 cases have shown improvement in clinical indicators and symptoms, a health official said Friday.

Up to 544 doses of plasma from convalescent COVID-19 patients have been collected across the country for treatment, said Guo Yanhong, an official with the National Health Commission (NHC) at a press conference Friday.

The plasma therapy has proved safe and effective, Guo added.

China has established expert task force at the provincial and national levels respectively to analyze and improve the use of plasma therapy, Guo said, adding the NHC is working with other authorities to motivate more convalescent patients to donate plasma.