A "historic breakthrough" in defiance of scientific rigor? US President Donald Trump welcomed on Sunday August 23 the decision of the US Medicines Agency (the FDA) to authorize "urgently" the large-scale use of blood plasma from people cured of Covid -19 to treat patients infected with the coronavirus. But this administrative green light has caused confusion within a part of the scientific community which emphasizes that there is not yet definitive proof of the effectiveness of this type of treatment. 

The FDA recalled that this technique had already been used on more than 70,000 patients, either in critical condition or in clinical trials, since the start of the Covid-19 pandemic in the United States. The US agency claimed that all tests performed suggest that patients who receive blood plasma containing a large number of antibodies have a significantly higher chance of surviving the disease than people who received plasma low in antibodies. It did not take more for Donald Trump to qualify this treatment as "historic breakthrough" which would save "a considerable number" of people.

A treatment used since the end of the 19th  century

It has been several months since the use of blood plasma from individuals who have survived Covid-19 has been one of the most promising treatment avenues, and some scientists even speak of "liquid gold", due to the golden color of the plasma. Several countries, including France, Austria and China, have also authorized the use of this treatment under certain conditions. "Clinical research and use in hospitals indicate, in fact, that blood plasma transfusions can reduce hospital stay and lower the death rate," says Joakim Dillner, epidemiologist at the Karolinska Institute in Stockholm , contacted by France 24.

The principle is simple: people who have overcome the disease donate their blood, from which the plasma is extracted. It is then necessary to ensure that this fluid used to transport blood cells contains enough antibodies before injecting it into infected patients in order to boost their own defense against the disease. "We administer one dose per day as long as the virus is present in the body," said Joakim Dillner, who found that "any presence of Covid-19 could disappear in two days".

This technique has been used since the end of the 19th century to fight against certain viral or bacteriological infections. It has, in particular, been experienced in the fight against the Ebola virus and during previous coronavirus epidemics (Sars in 2002 and Mers-Cov in 2012). But its effectiveness has never been 100% proven.

Clinical trials difficult to conduct

And this is still the case with the Covid-19. "What is missing is a randomized [randomized] controlled trial and it is very unusual for the FDA to approve a treatment without waiting for the results of such a test," said Stephen Evans, pharmacoepidemiology researcher in the department of statistics from the School of Hygiene and Tropical Medicine in London, contacted by France 24. This type of test is the holy grail of medical research because "without this phase we cannot be sure that it is indeed the recourse. to blood plasma which is at the origin of the improvement of the patient's condition and not another factor ", notes the British researcher. This method "makes it possible to ensure that we have not overestimated the effectiveness of a promising treatment", summarizes Joakim Dillner.

The problem with randomized controlled trials for blood plasma treatments is the difficulty of conducting them. We must recruit a large number of volunteers from hospitalized patients and obtain enough plasma from ex-patients, which means that the epidemic must already be in an advanced phase, recalls Joakim Dillner. In addition, "it is also necessary to know how to measure the number of antibodies necessary in the plasma for the treatment to be effective, which is difficult to do", adds the Swedish scientist. This is why, in the past, these tests were never successful before the end of epidemics.

With Covid-19, the world does not have the luxury of waiting, believes this scientist who understands the FDA's decision to have taken liberties with the traditional validation procedure. A point of view that is not shared by Stephen Evans. According to him, the American drug agency dealt a terrible blow to the work of scientists. "It is going to be much more difficult to do randomized blood plasma trials now because patients are going to prefer to receive the treatment in the hospital rather than volunteering for a randomized clinical trial where they will not be sure they are in. the group to which the right treatment will be administered ", he regrets.

But for Donald Trump, the time for scientific research is incompatible with his electoral calendar. The FDA gave him a tremendous gift as the Republican convention begins Monday that officially nominated him as the party's candidate for the US presidential election in November.

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