A search for clear answers
Treatments that target the early stages of COVID-19 “remain elusive. Few strategies provide benefit, several have failed, and others are being evaluated,” the researchers noted. “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 and, consequently, the most appropriate antibody concentrations for effective treatment are unclear.”
To learn more, Dr. Polack and colleagues included patients with PCR-confirmed COVID-19 who were aged 75 years or older, regardless of comorbidities. They also included patients aged 65-74 years who had at least one underlying condition. Participants were enrolled at clinical sites or geriatric units in Argentina. The mean age was 77 years, and 62% were women.
In an intent-to-treat analysis, the primary outcome – severe respiratory disease – occurred in 16% of the plasma recipients, vs. 31% of the group that received placebo. The relative risk was 0.52 (95% confidence interval, 0.29-0.94; P = .03).
The number needed to treat to avoid a severe respiratory disease episode was 7 (95% CI, 4-50).
Life-threatening respiratory disease, a secondary outcome, occurred in four people in the plasma group, compared with 10 in the placebo group. Two patients in the treatment group and four patients in the placebo group died.
The researchers also ran a modified intent-to-treat analysis that excluded six participants who experienced severe respiratory disease prior to receiving plasma or placebo. In this analysis, efficacy of plasma therapy increased to 60%.
“Again, this finding suggests that early intervention is critical for efficacy,” the investigators noted.
The investigators, who are based in Argentina, defined their primary endpoint as a respiratory rate of 30 or more breaths per minute and/or an oxygen saturation of less than 93% while breathing ambient air.
Dr. Sullivan pointed out that this is equivalent to the threshold commonly used for hospitalizing people with COVID-19 in the United States. “So it’s equivalent to avoiding hospitalizations. The take-home is high-titer plasma prevents respiratory distress, which equals hospitalization for us.”
Dr. Sullivan is conducting similar research in the United States regarding the use of plasma for treatment or prevention. He and colleagues are evaluating adults aged 18-90 years, “not just the ones at highest risk for going to the hospital,” he said. Enrollment is ongoing.
An inexpensive therapy with global potential?
“Although our trial lacked the statistical power to discern long-term outcomes, the convalescent plasma group appeared to have better outcomes than the placebo group with respect to all secondary endpoints,” the researchers wrote. “Our findings underscore the need to return to the classic approach of treating acute viral infections early, and they define IgG targets that facilitate donor selection.”
Dr. Polack said, “This is an inexpensive solution to mitigate the burden of severe illness in the population most vulnerable to the virus: the elderly. And it has the attraction of being applicable not only in industrialized countries but in many areas of the developing world.”
Convalescent plasma “is a potentially inexpensive alternative to monoclonal antibodies,” the researchers added. Furthermore, “early infusions of convalescent plasma can provide a bridge to recovery for at-risk patients until vaccines become widely available.”
Dr. Polack said the study findings did not surprise him. “We always thought that, as it has been the case in the past with many therapeutic strategies against respiratory and other viral infections, the earlier you treat, the better.
“We just hoped that within 72 hours of symptoms we would be treating early enough – remember that there is a 4- to 5-day incubation period that the virus leverages before the first symptom – and with enough antibody,” he added.
“We are glad it worked,” he said.
The study was supported by the Bill and Melinda Gates Foundation and by the Fundación INFANT Pandemic Fund. Dr. Polack, Dr. Simonovich, and Dr. Sullivan have disclosed various financial relationships industry.
A version of this article first appeared on Medscape.com.