Coronavirus

What is convalescent plasma and how can it be used to treat Covid-19?

The FDA has issued an Emergency Use Authorisation for convalescent plasma, saying it is safe and has promise as a treatmentn for the novel coronavirus.

What is convalescent plasma and how can it be used to treat Covid-19?
Lindsey Wasson REUTERS

People who have fully recovered from Covid-19 for at least two weeks are being encouraged to consider donating blood to allow doctors to extract plasma - containing antibodies to the coronavirus - which can then be used to treat patients suffering from the disease.

So far no drug has been approved by authorities as a safe and effective to cure the coronavirus but doctors are hopeful that the antibodies of people who have recovered from Covid-19 may be a possible effective treatment. 

Researches hope that the blood plasma, known as convalescent plasma, can be given to people with severe symptoms of Covid-19 to boost their ability to fight the Covid-19, preventing serious illness or death, while it might also help keep people who are moderately ill from becoming sicker.

On Sunday, the US Food and Drug Administration issued an Emergency Use Authorization (EUA) for convalescent plasma to treat the coronavirus. This EUA "authorizes the distribution of COVID-19 convalescent plasma in the U.S. and its administration by health care providers, as appropriate, to treat suspected or laboratory-confirmed COVID-19 in hospitalized patients with COVID-19," say the FDA.

President Donald Trump announced the issuance of the EUA at the White House on Sunday night.

The UK announced an actual clinical trial of blood plasma at the start of May, but it has not yet released results.

Limited supply of convalescent plasma

The FDA says that the “known potential benefits of the product outweigh the known and potential risks of the product.” Since the start of the program to test convalescent plasma therapy more than 70,000 patients have been given the treatment, with the FDA saying that these observational studies showed that convalescent plasma was "safe" and had "promise" as a treatment. These studies are not the more rigorous, peer-reviewed studies that would allow the treatment to be authorised. 

"The data we gathered suggests that patients who were treated early in their disease course, within three days of being diagnosed, with plasma containing high levels of antibodies, benefited the most from treatment. We saw about a 35% better survival in the patients who benefited most from the treatment," Alex Azar, Secretary of Health and Human Services, told a White House briefing. It should be noted that the patients were under 80 and not on a respirator. Azar also did not mention what the actual mortality rate in the cohort being studied was.

Even if convalescent plasma does prove to be an effective treatment for Covid-19, experts are warning that supplies of the product will be limited, due to the need for donors who have recovered from the virus to give blood. Furthermore, the number of antibodies in recovered patients' blood appears to fall fairly rapidly in many individuals, meaning the blood of patients who recovered some time ago may not contain enough antibodies to produce effective plasma.