A single dose of antibodies drawn from the blood of coronavirus survivors appears to have improved the symptoms of 10 patients severely ill with the disease, according to new research.
The treatment, known as convalescent plasma (CP) therapy, involves using antibody-rich blood plasma of those who have recovered from coronavirus, which can neutralise the bug to fight infection.
Scientists in China who conducted the preliminary study said no serious adverse reactions were observed after CP transfusion.
They believe the findings, published in the journal Proceedings of the National Academy of Sciences, suggest that CP therapy might be a safe and promising treatment for severe Covid-19 patients, and add further investigation is needed in controlled clinical trials.
But experts have warned the results, while encouraging, should be treated with caution.
Sir Munir Pirmohamed, president of the British Pharmacological Society, said: "This was not a randomised trial and all patients also received other treatments including antivirals such as remdesivir, which are currently in trials for Covid-19."
He added that it was also important to remember that there are potential safety concerns around the treatment, including diseases that occur through transfusion.
Sir Munir said: "Even if shown to work, scalability to treat large numbers of patients may become an issue."
The pilot study involved 10 patients, aged between 34 and 78, who showed severe symptoms such as shortness of breath and chest pain.
The enrolled patients received transfusion of a 200ml dose of CP.
The researchers said all clinical symptoms, which also included fever and cough, subsided within three days.
The patients' liver and lung function as well as blood oxygen levels were also found to have improved.
The numbers of disease-fighting white blood cells, lymphocytes, also increased, and antibody levels remained high after CP transfusion, the researchers said.
Meanwhile another study, reported in the Journal of the American Medical Association last month, showed that five critically ill coronavirus patients in Shenzen, China, improved after treatment with CP.
The Food and Drug Administration in the US approved the use of CT therapy as an experimental treatment in clinical trials, and for critical patients without other options.
In the UK, it has been reported that the NHS may start giving the therapy to hospital patients in the near future.
