Administering convalescent plasma that has high levels of antibodies against SARS-CoV-2 within the first 3 days of symptoms was associated with significantly lower chances of progression to severe COVID-19, new evidence demonstrates.
In a trial of 160 older adults with COVID-19, half of whom were randomly assigned to receive plasma and half to receive placebo infusion, treatment with high-titer plasma lowered the relative risk for severe disease by 48% in an intent-to-treat analysis.
“We now have evidence, in the context of a small but well-designed study, that convalescent plasma with high titers of antibody against SARS-CoV-2 administered in the first 3 days of mild symptoms to infected elderly reduces progression of illness and the rate of severe presentations,” senior author Fernando Polack, MD, said in an interview.
“Not any plasma, not any time,” added Dr. Polack, an infectious disease specialist and scientific director at Fundacion INFANT and professor of pediatrics at the University of Buenos Aires. The key, he said, is to select plasma in the upper 28th percentile of IgG antibody concentrations and to administer therapy prior to disease progression.
The study was published online Jan. 6 in The New England Journal of Medicine.
“It’s a very good study and approaches a different population from the PlasmAr study,” Ventura Simonovich, MD, chief of the clinical pharmacology section, Medical Clinic Service, Hospital Italiano de Buenos Aires, said in an interview. “This is the first published randomized controlled trial that shows real benefit in this [older adult] population, the most vulnerable in this disease,” he said.
Dr. Simonovich, who was not affiliated with the current study, was lead author of the PlasmAr trial, which was published in The New England Journal of Medicine Nov. 24, 2020. In that trial, the researchers evaluated adults aged 18 years and older and found no significant benefit with convalescent plasma treatment over placebo for patients with COVID-19 and severe pneumonia.
“We know antibodies work best when given early and in high dose. This is one of the rare reports that validates it in the outpatient setting,” David Sullivan, MD, professor of molecular biology and immunology at Johns Hopkins Bloomberg School of Public Health, Baltimore, said in an interview when asked to comment.
Dr. Sullivan pointed out that most previous studies on convalescent plasma focused on patients with COVID-19 who had severe cases late in the disease course.
Regarding the current study, he said, “The striking thing is treating people within 3 days of illness.”
A more cautious interpretation may be warranted, one expert said. “The study demonstrates the benefit of early intervention. There was a dose-dependent effect, with higher titers providing a greater benefit,” Manoj Menon, MD, MPH, a hematologist and oncologist at the University of Washington, Seattle, said in an interview.
“Taken together, the findings have biologic plausibility and produce more data on the role of convalescent plasma to a relevant age cohort,” he added.
However, Dr. Menon said: “Given the limited sample size, I do not think this study, although well conducted, definitively addresses the role of convalescent plasma for COVID-19. But it does merit additional study.”