More than 64,000 patients in U.S have received convalescent plasma, a century-old procedure that was used to help prevent influenza and measles before the respective vaccines appeared. It is a method that is used when new diseases appear, and history suggests that it works against some infections, but not all.
There is no solid evidence yet that plasma works to fight coronavirus and, if so, how best to use it. However, preliminary information from 35,000 coronavirus patients treated with plasma provides what Mayo Clinic principal investigator Dr. Michael Joyner said Friday are “Evidence of efficacy”.
There were fewer deaths among people who received plasma no later than three days after diagnosis, and also among those who were given plasma with the highest levels of virus-fighting antibodies, Joyner and colleagues reported.
The problem is that it was not a formal study. Patients were cared for in a variety of ways in hospitals across the country as part of a Food and Drug Administration (FDA) program designed to expedite access to experimental therapies. This so-called “expanded access” program tracks the effects achieved on beneficiaries, but cannot prove that plasma — and not other care received — was the real reason for the improvement.
Rigorous studies underway across the country are designed to obtain that evidence, by comparing similar patients randomly chosen to provide plasma or a placebo infusion in addition to routine care. However, those studies have been difficult to complete because the presence of the virus increases and decreases in different cities. Also, some patients have requested plasma rather than agree to inclusion in a study where they could be given a placebo.
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“For 102 years we have been debating whether convalescent plasma works or not,” said Dr. Mila Ortigoza of New York University, referring to the one used during the 1918 flu pandemic. This time “we really need a test. irrefutable”.
Ortigoza co-directs one of those studies, which this week is being expanded to three other states: Connecticut, Florida and Texas. Her team is also working to share information with other clinical trials in other regions, hoping to find answers more quickly.
“There is concern about when there will be a clear answer,” said Dr. Jeffrey Henderson, an infectious disease specialist at Washington University in St. Louis.
He expressed confidence that clinical trials will make progress on this issue, but noted that the Mayo Clinic report is consistent with earlier, smaller plasma studies and “an example of how to do the best you can with the information available. ”.
When the body faces a new germ it produces proteins called antibodies specially designed to fight that particular infection. Antibodies are found in plasma, which is the yellowish, liquid part of the blood. Since the formation of antibodies takes a few weeks, the hope is that the transfusion of antibodies from another person can help patients fight the virus before their immune system kicks in.
The Mayo Clinic findings were published online before being scrutinized by other scientists. They show that 20% of people who were given plasma with high levels of antibodies no later than three days after diagnosis had died before 30 days, compared with 30% of people treated later with plasma that had fewer of antibodies.
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The FDA has been carefully weighing whether the evidence is good enough to allow the so-called emergency use of convalescent plasma, a move that would make it even more difficult to complete more rigorous testing. The FDA did not comment on the matter Friday.
Tens of thousands of COVID-19 survivors have donated plasma, and blood banks have urged others to do so as well in order to meet the demand, as the coronavirus continues to wreak havoc in the United States. According to the AABB, the American Association of Blood Banks, a quarter of the hospitals that it monitors weekly are reporting waits of more than 24 hours to obtain the requested plasma.
Beyond whether plasma helps in general, scientists want to know when it should be used, in very sick people or in those who show the first signs of infection. And what is the correct dosage.
COVID-19 survivors have varying amounts of antibodies, which Ortigoza said are difficult to measure before using donated plasma. The specialist indicated that another question is which of the many types of antibodies are the best to be used.
Joyner stressed that the expanded access program was not intended to replace rigorous studies, but was originally designed to track 5,000 people and verify the safety of plasma use. However, use of the program soared.
“There is possibly reasonable and actionable evidence from our findings to reinforce” the historical lessons of plasma therapy, that the sooner it is applied the better, he added.