"Two patients were given plasma on Tuesday, while two were given the therapy on Thursday. The two patients who received plasma on Tuesday have shown improvement," Kejriwal told the media here.
"Next week, we will seek central government permission to try the therapy on all the serious corona patients in Delhi," Kejriwal said, pointing out that these are "just the initial results".
Last Tuesday, the Delhi government had got the approval from the Centre to try plasma therapy on critical patients.
In the fight against the coronavirus, Kejriwal said, his government is fighting on two levels -- to control the spread of the infection and also to treat those who have the infection.
In convalescent plasma therapy, antibodies of a recovered patient are taken and transfused into a sick person (infected by the virus) to help boost the latter's immune system.
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Dr S.K. Sarin, head of Institute of Liver and Biliary Sciences (ILBS), told the media that they were hopeful that more people could be given the therapy.
"Also, among the four, at least two may be discharged by the weekend," Sarin said.
He said those who have recovered from the disease should step forward to donate plasma to treat others.
"Only the plasma is taken and not the blood. The donor can donate plasma after an interval of 10-12 days, unlike blood donations, which can be done only once in three months," Dr Sarin said.
He said that 25 persons need plasma donation at present. "It is inexpensive and affordable, unlike medications which are costly."
Urging people to step forward for plasma donation, Kejriwal said: "We will not take blood but only plasma. Your blood will be put back in the body after the plasma is separated and used.
"We are giving it to very serious patients. We are saving lives with this. You will help serious patients. We are making all arrangements for those willing to donate."
Kejriwal said all recovered patients will get a call from the government if they wish to donate their plasma.
He said a private Delhi hospital also had tried the therapy and got positive result.
The Max Hospital in Saket had used plasma therapy on a critical coronavirus patient. The treatment showed positive results and the patient was taken off ventilator support, the hospital said on Monday. The 49-year-old man was the first corona patient administered plasma at the hospital.
Delhi has reported about 2,400 coronavirus cases and 50 deaths so far.