New York,  A new trial has found that convalescent plasma therapy is a safe treatment option for patients with severe Covid-19 synptoms, say researchers as globally the coronavirus infection has affected over 6 lakh people and at least half of them have succumbed to the pandemic.

For the findings, published in The American Journal of Pathology, researchers from the Houston Methodist Hospital in the US, began clinical trials to transfuse plasma from recovered Covid-19 patients into critically ill patients on March 28.

Results of the trial showed that 19 out of 25 patients (76 per cent) improved with the treatment and 11 were discharged from the hospital. There were no serious adverse side effects caused by the plasma transfusion.

"While physician-scientists around the world scramble to test new drugs and treatments against the Covid-19 virus, convalescent serum therapy emerge as potentially one of the most promising strategies," said study researcher Eric Salazar from Houston Methodist Hospital.

Patients were treated under emergency use guidelines (eIND) from the US Food and Drug Administration and then received approval from the FDA to open up the trial to more patients as an investigational new drug (IND).

According to the researchers, the century-old therapeutic approach dates back to at least as early as 1918 when it was used to fight the Spanish Flu. Recently, they added that convalescent plasma therapy was used with some success during the 2003 SARS pandemic, the 2009 influenza H1N1 pandemic, and the 2015 Ebola outbreak in Africa.

Following a study early on in the Covid-19 pandemic, where a handful of critically ill patients in China showed an improvement, an interdisciplinary team of Houston Methodist physician-scientists and health care workers rapidly targeted the Covid-19 virus with convalescent serum therapy.

Additional findings during this trial revealed patient outcomes following plasma therapy were very similar to recently published results of patients treated on a compassionate-use basis with the antiviral drug remdesivir.

The research team also concluded that any observed complications were consistent with findings reported for Covid-19 disease progression and did not result from the plasma transfusions.

The overall findings were consistent with several other small case studies of convalescent plasma use for severe Covid-19 that have been recently reported.

Although the convalescent plasma therapy administered on the front lines at Houston Methodist was implemented for emergency treatment, they said there is an immediate need for controlled clinical trials to determine its efficacy.

Researchers are considering a randomised controlled trial to look more closely at variables such as the timing of the transfusion after the onset of symptoms.

Earlier, a study published in the International Journal of Risk & Safety in Medicine, revealed that passive vaccine or passive immunization (PI) can provide instant, short-term fortification against infectious agents and slow down Covid-19.