Study hints but can’t prove that survivor plasma fights COVID-19
Mayo Clinic researchers reported a strong hint that blood plasma from COVID-19 survivors helps other patients recover, but it’s not proof and some experts worry whether, amid clamor for the treatment, they’ll ever get a clear answer.
More than 64,000 patients in the U.S. have been given convalescent plasma, a century-old approach to fend off flu and measles before vaccines. It’s a go-to tactic when new diseases come along, and history suggests it works against some, but not all, infections.
There’s no solid evidence yet that it fights the coronavirus and, if so, how best to use it. But preliminary data from 35,000 coronavirus patients treated with plasma offers what Mayo lead researcher Dr. Michael
Joyner on Friday called “signals of efficacy.”
There were fewer deaths among people given plasma within three days of diagnosis and also among those given plasma containing the highest levels of virus-fighting antibodies, Joyner and colleagues reported.
The problem: This wasn’t a formal study. The patients were treated in different ways in hospitals around the country as part of a Food and Drug Administration program designed to speed access to the experimental therapy. That so-called “expanded access” program tracks what happens to the recipients, but it cannot prove the plasma – and not other care they received – was the real reason for improvement.
Rigorous studies underway around the country are designed to get that proof, by comparing similar patients randomly assigned to get plasma or a dummy infusion in addition to regular care. But those studies have been difficult to finish as the virus waxes and wanes in different cities. Also, some patients have requested plasma rather than agreeing to a study that might give them a placebo instead.
“For 102 years we’ve been debating whether or not convalescent plasma works,” said Dr. Mila Ortigoza of New York University, referring to plasma’s use in the 1918 flu pandemic. This time around, “we really need undisputable evidence.”
Ortigoza is co-leading one such study, which this week is expanding to Connecticut, Florida and Texas. Her team also is working to pool data with several other clinical trials in other regions, in hopes of faster answers.
When the body encounters a new germ, it makes proteins called antibodies that are specially targeted to fight that particular infection. The antibodies float in plasma – the yellowish, liquid part of blood. Because it takes a few weeks for antibodies to form, the hope is that transfusing someone else’s antibodies could help patients fight the virus before their own immune system kicks in.
The Mayo findings were posted online ahead of scientific peer review. They show that 20% of people given high-antibody plasma within three days of diagnosis had died within 30 days compared with 30% of people treated later with low-antibody plasma.