COVID-19: Ivermectin fails, convalescent plasma succeeds

Two gold-standard trials published in The New England Journal of Medicine on Wednesday help settle questions about two controversial therapies touted by many early in the pandemic with decidedly mixed results – failure for the antiparasite drug ivermectin and success for antibody-rich blood plasma from COVID-19 survivors.

In Brazil, 3,515 patients with symptoms of COVID-19 for a week or less and at least one risk factor for serious disease were randomly assigned to receive ivermectin once daily for three days, another treatment, or a placebo. Four weeks later, ivermectin failed to lead to a lower rate of hospitalization or prolonged emergency room visits, the researchers reported.

The horse dewormer was popular with conservative commentators and anti-vaccine people despite warnings from health officials not to use it to treat COVID.

For the study of so-called convalescent plasma, U.S. researchers enrolled more than 1,000 mostly unvaccinated adults within eight days of the onset of COVID-19 symptoms. Half of the participants were randomly assigned to receive a convalescent-plasma transfusion. Four weeks later, 2.9% of those who received the plasma had been hospitalized for COVID-19, compared to 6.3% of those who did not receive it. After accounting for individuals’ risk factors, the treatment reduced the risk of hospitalization by 54%, the researchers said.

“COVID-19 convalescent plasma is available in low-income and middle-income countries, has no patent limitations, and is relatively inexpensive to produce … (and probably) less vulnerable to the emergence of antibody resistance,” they added.