Eleven critically ill patients at a hospital in Wuhan received plasma infusions last week: one patient has already been discharged, one is able to get off the bed and walk and the others are all recovering .

Chinese health officials Monday urged patients who have recovered from the coronavirus to donate blood so that plasma can be extracted to treat others who are critically ill.

Drugmakers are racing to develop a vaccine and treatment for the epidemic, which has killed 1,770 people and infected over 70,500 people across China.

Plasma from patients who have recovered from a spell of pneumonia triggered by COVID-19 contains antibodies that can help reduce the virus load in critically ill patients, an official from China’s National Health Commission told a press briefing Monday.

“I would like to make a call to all cured patients to donate their plasma so that they can bring hope to critically ill patients,” said Guo Yanhong, who heads the NHC’s medical administration department.

Eleven patients at a hospital in Wuhan—the epicentre of the disease—received plasma infusions last week, said Sun Yanrong, of the Biological Center at the Ministry of Science and Technology.

“One patient (among them) has already been discharged, one is able to get off the bed and walk and the others are all recovering,” she said.

The call comes days after China’s state-owned medical products maker reported successful results from its trial at Wuhan First People’s Hospital.

China National Biotec Group Co. said in a post on its official WeChat account that severely ill patients receiving plasma infusions “improved within 24 hours”.

The World Health Organization said exploring the use of plasma as a treatment for the novel coronavirus was “important”, but cautioned it needed to be done “with safety”.

“It is a very important area of discovery,” head of WHO’s emergencies programme Michael Ryan told reporters in Geneva, pointing out that plasma had proven effective in saving lives when combatting a range of different diseases.

“It is a very valid way to explore therapeutics, especially when we don’t have vaccines and we don’t have specific anti-virals,” he said.

His colleague Sylvie Briand, who heads WHO’s Global Infectious Hazard Preparedness division, meanwhile cautioned that plasma-based treatments could be difficult to scale up to reach large numbers of patients, and stressed the need to carefully follow safety protocols.

“With blood products you can also transmit other diseases, so the protocol … is very important,” she told reporters.

Sun stressed that “clinical studies have shown that infusing plasma (from recovered patients) is safe and effective.”

Blood donors will undergo a test to ensure that they are not carrying the virus, said Wang Guiqiang, chief physician at Peking University First Hospital.

“Only plasma is taken, not all the blood,” he said.

“Other components of the blood including red blood cells and platelets will be infused back into the donors.”