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The FDA limited the scope of authorized COVID-19 convalescent plasma use to a subset of hospitalized patients, in a .

According to the updated emergency use authorization (EUA), only high-titer convalescent plasma should be used, and only for a narrower population: hospitalized patients early in disease course and those with impaired humoral immunity who cannot produce an adequate endogenous antibody response. Low-titer convalescent plasma is no longer authorized for use.

These recommendations were based on updated data from clinical trials, the FDA said, specifically citing research from the expanded access protocol from the Mayo Clinic, as well as other smaller trials.

Data from the Mayo Clinic trial was published in an August preprint, but not in a peer-reviewed journal until January. The journal publication indicated that higher-titer plasma was associated with a lower risk of death than lower-titer plasma, and patients receiving the treatment who were non-mechanically ventilated had a lower risk of death than those receiving mechanical ventilation.

"Based on assessment of these data, potential clinical benefit of transfusion of COVID-19 convalescent plasma in hospitalized patients with COVID-19 is associated with high titer units administered early in the course of disease," the agency wrote. "Transfusion of COVID-19 convalescent plasma in hospitalized patients late in the course of illness (e.g., following respiratory failure requiring intubation and mechanical ventilation) has not been associated with clinical benefit."

A has also been updated to include this information about lack of clinical benefit in intubated patients.

Controversy has always followed use of convalescent plasma for COVID-19, which was authorized in August a day after a tweet from President Trump to former FDA Commissioner Stephen Hahn, MD, nudging him about its authorization. Hahn was later forced to walk back certain claims he made about the treatment at a press conference, which had exaggerated the clinical benefit.

The EUA for convalescent plasma was revised at least once before. In November, the agency added a requirement for an additional test in convalescent plasma manufacture to qualify high-titer plasma. Nine tests are now authorized for this purpose, the FDA said.

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