A coronavirus treatment that has already been approved in the UK has helped patients recover within three days.
Convalescent plasma therapy involves giving people a dose of blood donated by Covid-19 survivors, which contains the antibodies their immune system needs to fight off the virus.
The technique was first introduced a century ago during the Spanish flu pandemic, and is already being used in China, Italy and the US.
Dr Mike Ryan, head of the World Health Organisation 's health emergencies program, has labelled the potentially lifesaving treatment a "very important area to pursue".
There's still not enough evidence to say if it will be effective to large populations, but a test in Wuhan has provided a positive sign.
A pilot study in Wuhan (the epicentre of the pandemic) saw ten severely ill patients who had been given plasma therapy have their symptoms vanish or vastly improve less than 72 hours later.
The patients' liver and lung function as well as blood oxygen levels improved, signs they had successfully fought off the virus.
Of the ten, three were discharged from hospital and the rest were ready for discharge by the end of the study.
In comparison, a control group of ten patients in a similar condition were not given the therapy. Of that group three people died, six saw their conditions stabilise and only one improved over the course of the study.
The blood therapy is considerably cheaper than developing a new drug, and only requires drawing blood from a recovered patient.
It takes that patient's antibodies, which are only created in bodies that have learned how to fight off the virus, and injects them into someone currently ill to boost their immune system.
The same treatment was used in the SARS and MERS outbreaks as well on Ebola patients.
Professor Sir Munir Pirmohamed, President of the British Pharmacological Society, said the findings should be taken with caution as it was not a randomised trial and all patients were given additional drugs.
While there were no side effects reported, there are potential risks to the treatment including dangerous conditions being passed to patients through transmission.
The Medicines and Healthcare products Regulatory Agency (MHRA) approved the therapy in early March, meaning NHS patients will be able to get the treatment.