Health Experts Say Convalescent Plasma Therapy Require More Studies

More than 70,000 patients in the US 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.

The Mayo Clinic reported preliminary data from 35,000 coronavirus patients treated with plasma, and said 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.

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But it wasn’t a formal study. The patients were treated in different ways in hospitals around the country as part of an FDA program designed to speed access to the experimental therapy.

That “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.

Administration officials, in a call with reporters Sunday, discussed a benefit for patients who were within three days of admission to a hospital and were not on a respirator, and were given ‘high-titer’ convalescent plasma containing higher concentrations of antibodies.

They were then compared to similar patients who were given lower-titer plasma. The findings suggest deaths were 35 percent lower in the high-titer group.

There’s been little data on how effective it is or whether it must be administered fairly early in an illness to make a significant difference, said Dr. William Schaffner, an infectious diseases expert at Vanderbilt University.

Aiming to ward off a possible run on convalescent plasma after the announcement, government officials have been working to obtain plasma and to team with corporate partners and nonprofit organizations to generate interest among previously infected patients to donate.