Buenos Aires, Argentina—Convalescent plasma administered to patients hospitalized with COVID-19 was not beneficial—another disappointment in the effort to find helpful therapies to fight the novel coronavirus.

A new study suggests the problem might have been that antibodies had been administered too late in the course of the illness and, instead, tested their use in older patients early on. Results published in The New England Journal of Medicine include some promising signs.

Declaring that “therapies to interrupt the progression of early coronavirus disease 2019 (Covid-19) remain elusive,” an international team of researchers conducted a randomized, double-blind, placebo-controlled trial of convalescent plasma with high IgG titers against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in older adult patients. They received the plasma within 72 hours after the onset of mild Covid-19 symptoms.

Defined as the primary end point was severe respiratory disease—i.e., respiratory rate of 30 breaths per minute or more, an oxygen saturation of less than 93% while the patient was breathing ambient air, or both. Researchers report their trial was stopped early at 76% of its projected sample size because cases of COVID-19 in the trial region decreased considerably and steady enrollment of trial patients became virtually impossible.

With 160 patients undergoing randomization, in the intention-to-treat population, severe respiratory disease developed in 13 of 80 patients (16%) who received convalescent plasma and 25 of 80 patients (31%) who received placebo (relative risk, 0.52; 95% CI, 0.29-0.94; P = .03), with a relative risk reduction of 48%.

In addition, a modified intention-to-treat analysis that excluded six patients who had a primary end point event before infusion of convalescent plasma or placebo showed a larger effect size (relative risk, 0.40; 95% CI, 0.20-0.81). No solicited adverse events were observed, according to the report.

“Early administration of high-titer convalescent plasma against SARS-CoV-2 to mildly ill infected older adults reduced the progression of COVID-19,” the authors conclude.

Background information in the articles points out that, among the strategies under investigation to treat novel coronavirus, is the infusion of specific antibodies from patients, adding, “plasma infusions have not been commonly associated with adverse events and have been associated with improved outcomes in patients who have had other diseases. However, antibodies in plasma must be administered soon after infection in order to be effective.”

Researchers further point out that, in hospitalized patients with COVID-19, the infusion of convalescent plasma against SARS-CoV-2 late in the course of illness has not shown clear benefits.

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