New Delhi: Convalescent plasma therapy, which uses the blood of recovered COVID-19 patients as a potential treatment, has shown limited effect in reducing the progression to severe disease or death in a trial conducted in India, scientists say.
The study, published on Thursday in the British Medical Journal (BMJ), involved 464 adults with moderate COVID-19 who were admitted to hospitals in India between April and July.
As many as 239 adult patients received two transfusions of convalescent plasma, 24 hours apart, alongside standard care, while the control group comprising of 229 patients received standard care only.
One month later, 44 patients or 19 per cent of those who received the plasma had progressed to severe disease or had died of any cause, compared with 41 patients or 18 per cent in the control group.
Plasma therapy did, however, seem to reduce symptoms, such as shortness of breath and fatigue, after seven days, according to the researchers, including those from Indian Council of Medical Research (ICMR), and National Institute of Epidemiology, Tami Nadu.
"Convalescent plasma was not associated with a reduction in progression to severe covid-19 or all cause mortality," the researchers wrote in the journal.
"This trial has high generalisability and approximates convalescent plasma use in real life settings with limited laboratory capacity," they said.
Professor Martin Landray, from the University of Oxford in the UK, noted that although there is substantial interest in convalescent plasma as a possible treatment for COVID-19, there remains considerable uncertainty about whether it is effective in tackling the worst effects of the disease.
"The paper reports the results of the largest randomised trial of convalescent plasma to complete so far. However, with just a few hundred patients, it is still much too small to give clear results," Landray said.
"It would need to be substantially larger to pick up a meaningful sign of benefit and even then there would still be questions about whether different types of patient respond better or worse," he added.
The researchers noted that a prior measurement of neutralising antibody titres in donors and participants might further clarify the role of convalescent plasma in the management of COVID-19.
Patients in the study were aged at least 18 years who had confirmed COVID-19 based on a RT-PCR result for SARS-CoV-2, the virus that causes the disease.
Participants in the intervention arm received two doses of 200 millilitre (mL) of convalescent plasma, transfused 24 hours apart, in addition to the best standard of care.
Although the observational studies conducted previously suggested clinical benefits in recipients of convalescent plasma, the trials were stopped early and failed to ascertain any mortality benefit from plasma treatment in patients with COVID-19, the researchers said.
The new study shows that in settings with limited laboratory capacity, convalescent plasma does not reduce 28 day mortality or progression to severe disease in patients admitted to hospital with moderate COVID-19, they said.
Although plasma treatment was associated with earlier resolution of shortness of breath and fatigue and higher negative conversion of SARS-CoV-2 RNA on day 7 of enrolment, as a potential treatment for patients with moderate COVID-19, it showed limited effectiveness.
"The poor performance of convalescent plasma in this trial is disappointing but not entirely surprising," said Professor Ian Jones, Professor of Virology, University of Reading in the UK.
"The treatment, which delivers antibodies from COVID survivors to infected persons is, in essence, intended as an anti-viral treatment and like all antivirals the window of opportunity to stop an acute infection is very short," Jones added.