Trials are underway to see whether blood products from people who have recovered from COVID-19 can help boost the immune response of people with severe infection.
People who have recovered from COVID-19 will have produced specific antibodies that target the virus and mark it out for destruction by other immune cells. These antibodies remain in the clear blood fluid (plasma) after they recover. Doctors are carrying out trials to find out whether giving an infusion of this ‘convalescent plasma’ from a donor could help people who are seriously ill. Convalescent plasma has been used to treat other respiratory viruses, including SARS, in the past.
To date, only a few observational reports are available on its use in COVID-19, which cannot provide good evidence. However, 22 randomised controlled trials are now underway, which should give more reliable results on whether this investigational product is a safe and effective treatment for COVID-19.
Where did the story come from?
Several media outlets (NBC and Mail Online) have reported on the use of convalescent plasma in hospitals. Healthcare services in the UK and US among other countries are asking people who have recovered from COVID-19 to register to donate their plasma. However, a Cochrane systematic review of studies completed so far said there was not yet enough evidence to say whether it works. Convalescent plasma is regulated as an investigational product, for use in trials currently.
What is the basis for the claim?
In late April, the Cochrane review searched for studies that reported using convalescent plasma to treat COVID-19. They identified eight observational studies, including 32 patients, most of whom needed respiratory support. Patients were followed up from between 3 and 37 days after transfusion.
None of the patients died during follow-up. Six studies reported seeing improvement in patient symptoms after transfusion. However, the quality of reporting was poor, and the researchers could not extract sufficient information about these improvements. Neither were the studies consistent in their reporting of admissions to intensive care, duration of stay, or discharges from hospital.
Therefore this provides very limited evidence on the effect of convalescent plasma. Because there was no comparison group of patients receiving standard or alternative care, we do not know whether any improvements were a direct result of the infusion. They might have been due to other treatment, or just reflected the natural course of the infection.
However, two patients in two studies experienced adverse reactions. One got a fever after having the infusion of convalescent plasma, while another had a serious allergic reaction. Therefore the risk-benefit balance also needs to be considered.
Encouragingly, the review identified 48 ongoing studies, 22 of which are randomised controlled trials. These should balance out any differences in patient characteristics and give more reliable information about whether convalescent plasma is a safe and effective treatment for COVID-19.
What do trusted sources say?
Earlier this month, the UK Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO) outlined the proposal to collect donated blood from individuals with 28 days of their recovery from COVID-19. The optimal donors are expected to be those who have been hospitalised with severe infection, as they would have produced the highest antibody levels.
The proposal highlights the current restriction that people who have been transfused since 1980 are not currently able to donate blood due to risk of vCJD transmission. This would mean that people who receive convalescent plasma could not then donate themselves, potentially limiting future donor numbers. They provisionally propose that these individuals should be allowed to donate as the risk is low.
Analysis by EIU Healthcare, supported by Reckitt Benckiser
Citation
- Valk SJ et al. Convalescent plasma or hyperimmune immunoglobulin for people with COVID-19: a rapid review. Cochrane Database of Systematic Reviews 2020, Issue 5. Art. No.: CD013600. DOI: 10.1002/14651858.CD013600.
Reading list
- Editorial. The resurgence of convalescent plasma therapy. The Lancet Haematology 2020; 7, e353.
- Department of Health and Social Care. Use of plasma donations to treat COVID-19: recommendations from SaBTO
- US Food and Drug Administration. Recommendations for Investigational COVID-19 Convalescent Plasma