Study: Early use of convalescent plasma for COVID-19 may improve outcome for some outpatients

Photo shows a bag of plasma held by healthcare worker.

When it comes to convalescent plasma for the treatment of COVID-19, early intervention appears to make a difference for some outpatients. That’s according to a new study published in the New England Journal of Medicine

A clinical trial comparing the efficacy and safety of COVID-19 convalescent plasma to placebo in adult outpatients who received early transfusion of the plasma -- within nine days of the onset of COVID-19 symptoms -- found that the patients receiving the plasma were significantly less likely to be hospitalized. The study raises new hopes that convalescent plasma may still be a viable option for use in some outpatients when administered soon after symptom onset, the researchers suggested.  

Conducted between June 2020 and October 2021, the nationwide multicenter trial included a total of 1,181 patients who were injected with either convalescent plasma or placebo.  Also known as “survivor’s plasma,” it is blood plasma derived from patients who have recovered from COVID-19 and contains antibodies to SARS-CoV-2, the virus that causes the disease.  
Of the participants who received placebo, 6.3% were hospitalized within 28 days, compared with 2.9% of those receiving convalescent plasma. That translates to a 54% risk reduction among convalescent plasma recipients, the research said. The study also found that if convalescent plasma is given even earlier -- within five days after diagnosis -- the treatment was 80% effective in reducing hospitalization. 

The trial contrasts with the results of a previous study conducted among 500 participants at 48 emergency departments in the United States, in which high-risk outpatients were given convalescent plasma within the first week of their symptoms. That study, called C3PO, was stopped early due to lack of efficacy. It found that high-titer (antibody-rich) convalescent plasma did not prevent disease progression to severe COVID-19 illness in this high-risk population, who had at least one risk factor for progression to severe COVID-19, such as obesity, hypertension, diabetes, heart disease, or chronic lung disease.  Unlike the C3PO study, the current study did not include this high-risk population.   
Researchers are continuing to look at factors that affect convalescent plasma use, including insufficient plasma dose, timing of plasma administration, host-related factors, or other aspects of the host tissue responses to the infection.