Convalescent plasma therapy for Covid-19 is an unproven and experimental treatment and should be used only as part of research, the Union health ministry said amid signs of enthusiasm for the therapy from sections of the public and AAP leaders in Delhi.

The ministry said the therapy – which uses plasma donated by patients who have recovered from Covid-19 – is among treatments still under evaluation. The Indian Council of Medical Research has started a national study to assess its efficacy as a treatment for Covid-19, it said.

“Until the ICMR concludes its study and robust scientific proof is available, it should not be used except for research purposes,” the ministry said in a statement. “In fact, the use of convalescent plasma therapy may have life-threatening complications.”

The ministry’s call for caution comes four days after Delhi chief minister Arvind Kejriwal signalled his government’s interest to provide convalescent plasma therapy to all serious patients if encouraging results on four patients are seen in two or three additional patients.

“We have tried the therapy on four patients and the results are satisfactory,” Kejriwal had said on Friday. “We’ve got permission for limited trials. After trials on two or three more patients, we will apply for permission for the therapy to be given to all serious corona patients across Delhi.”

Kejriwal tweeted on April 24: “Donating plasma is absolutely painless, hasslefree and no weakness experienced.”

But medical researchers, concerned about enthusiasm for the therapy among patients and their relatives, point out that the recovery of seriously-ill Covid-19 patients after receiving convalescent plasma therapy does not establish that they recovered because of the therapy.

The ICMR, in a post on Twitter, said despite the threat of the Covid-19 pandemic, there is need to ensure ethical integrity and establish the scientific basis of using convalescent plasma therapy in patients.

The health research agency had earlier this month said it had received 99 applications from research groups across India for a randomised controlled study to assess the safety and efficacy of convalescent plasma therapy in Covid-19 patients.

Convalescent plasma is an antibody-rich product from the blood donated by people who have recovered from the infection. The US Food and Drug Administration pointed out on April 13 that although promising, convalescent plasma has not yet been shown to be safe and effective as a treatment for Covid-19.

The FDA said experience with respiratory viruses and limited data from China suggest that convalescent plasma has the potential to lessen the severity or shorten the length of the illness caused by Covid-19.