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Convalescent plasma ‘potentially effective’ against COVID-19: Research
But experts advise against ‘cherry picking’ results from a small study, saying randomised controlled trials are still needed.
Experts maintain convalescent plasma might be a ‘promising’ treatment for COVID-19, but says more randomised controlled trials are needed.
Recent research published in Nature Medicine has found that COVID-19 patients treated with convalescent plasma were less likely to die before the completion of the study than those in the control group.
Those in the treatment group were also less likely to require oxygen two weeks following transfusion.
The retrospective case-control score-matched study examined 39 patients hospitalised with severe symptoms of COVID-19 in New York between 24 March and 8 April.
The study reported that, on the day of transfusion, 87% of patients required supplemental oxygen and 10% were on ventilators.
By day 14 following transfusion, 18% of the treatment group required more oxygen, while 28% of the control group required more oxygen.
By the end of study, 13% of the patients in the treatment group and 24% of the control group had died, and 72% and 67% from each group, respectively, had been discharged alive.
‘Overall, survival probability was greater in convalescent plasma recipients than controls,’ the study authors wrote.
‘Convalescent plasma is potentially effective against COVID-19, but adequately powered, randomised controlled trials are needed.’
The theory behind the use of this treatment is that the plasma of patients who have recovered from COVID-19 contains antibodies to parts of SARS-CoV-2. Their plasma – referred to as convalescent plasma – can then be given to newly infected patients via transfusion.
This may result in more rapid control and clearance of SARS-CoV-2.
Royal Melbourne Hospital infectious diseases clinician Associate Professor Steven Tong is the principal investigator for the AustralaSian COVID-19 Trial (ASCOT) and a co-lead of clinical research at the Doherty Institute.
He told newsGP this study had many limitations.
‘It’s an observational study of only 39 patients, so it suffers from the weaknesses of any retrospective observational study in that the patients are not randomised and it’s difficult to adjust for confounders between the active treatment group and any control patients,’ he said.
He says, however, the results are ‘promising’.
‘But I think you can’t cherry pick data from one study or another until we get sufficient data to make a more conclusive recommendation,’ he said.
While the results of this study seem encouraging, Associate Professor Tong says those of another recent study on convalescent plasma, the PLACID study, were less promising.
That randomised controlled trial involved 464 moderately ill COVID-19 patients infected and hospitalised with SARS-CoV-2 in India between 22 April and 14 July.
Of those, 235 were administered convalescent plasma coupled with standard of care, while 229 received solely the standard of care.
While that study has not been peer-reviewed, it found the use of convalescent plasma failed to reduce mortality or stop progression of severe COVID-19. However, Associate Professor Tong says there may be reasons convalescent plasma was not found to be effective in that trial.
‘There are some issues with that study in that the amount of neutralising antibodies in the donated plasma was often quite low,’ he said.
‘That may help to explain why there was a negative result.’
Rather than relying on the results of this new paper in Nature Medicine, Associate Professor Tong believes further randomised controlled clinical trials are required.
He says Australia is currently engaged in two such trials:
- ASCOT, designed to assess the effectiveness of convalescent plasma in hospitalised COVID-19 patients
- Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP), an Australian-led global study looking at the effect of convalescent plasma on COVID-19 patients on ventilators
Associate Professor Tong says the first Australian patient was recruited to ASCOT at the Royal Melbourne Hospital at the end of July and, as of the time of publication, there are 29 patients that have been randomised in ASCOT.
It is too early to start examining that data.
‘We’re not looking at that data because it’s not going to be meaningful at this stage,’ Associate Professor Tong said.
‘And in a clinical trial you don’t just start looking at data because it might influence your equipoise for randomising patients.’
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