AN ANTIBODY treatment hailed as a "major breakthrough" against Covid by President Donald Trump failed to reduce deaths or severe illness in clinical trials.

Convalescent plasma, donated by patients who have recovered from the virus and packed with their antibodies, has been effective in other infectious diseases such as measles and influenza.

Countries, including Britain, have been stockpiling blood plasma so the treatment could be rolled out if it proved effective, and in August President Trump issued an emergency authorisation to allow its use in the US.

Mr Trump went on to receive Regeneron, an experimental treatment created with laboratory-grown antibodies rather than donor plasma, when he contracted Covid earlier this month.

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However, a new randomised control study, published today in the British Medical Journal (BMJ), found that plasma transfusions made no difference to outcomes in Covid patients.

The study was carried out in India and involved 450 adults hospitalised with moderate illness.

Half received only standard treatment and half standard treatment plus convalescent plasma.

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In both groups around 20 per cent of patients progressed to severe illness or died from any cause, the researchers found.

Professor Aparna Mukherjee, of the Indian Council of Medical Research, who co-led the research, said: “As a potential treatment for patients with moderate covid-19, convalescent plasma showed limited effectiveness.

“Future research could explore using only plasma with high levels of neutralising antibodies, to see if this might be more effective.”