The Food and Drug Administration announced Sunday that it would approve the emergency use authorization, or EUA, of convalescent plasma to treat COVID-19 patients. But scientists say that the government’s action is premature since the treatment has not been proven safe and effective against the coronavirus and could hinder the development of crucial clinical trials to determine its efficacy.

According to Kaiser Health News, the century-old treatment, called convalescent plasma therapy or convalescent serum therapy, uses blood products taken from those who have recovered from a viral infection and injects them into those who are still suffering. The practice was first used to combat the 1918 flu pandemic and has since been used to treat victims of Ebola, SARS and H1N1 influenza.

But according to The Hill, in the case of SARS-CoV-2, the virus that causes COVID-19, there is conflicting evidence that the treatment even works.

“We are far from having any definitive proof that it’s effective, clinically, and saves lives,” said Dr. Howard Koh of the Harvard T. H. Chan School of Public Health. Several studies including three conducted by the Mayo Clinic, one in Wuhan, China, and another in the Netherlands led to mixed and inconclusive results, according to The Hill.

Francis Collins, director of the National Institutes of Health, and Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, both raised objections to the EUA issued by the Trump administration.

Experts pointed out that convalescent plasma treatment can be risky and even potentially deadly. Koh said that the government’s swift action without scientific evidence may prevent further studies to evaluate the efficacy and safety of using convalescent plasma to treat COVID-19 patients now that it’s available.

Interestingly, on Aug. 23, the same day it issued the EUA, the FDA posted recommendations for the use of convalescent plasma for COVID-19 patients.

“Although promising, convalescent plasma has not yet shown to be safe and effective as a treatment for COVID-19,” said the FDA on its website. “Therefore, it is important to study the safety and efficacy of COVID-19 convalescent plasma in clinical trials.”

Koh couldn’t agree more.

“The best way to move forward toward definitive outcomes is to have a randomized trial,” he said, according to The Hill, adding that the emergency authorization will “hamper our abilities to ever prove definitively that convalescent plasma works.”