Coronavirus patients who were hospitalised by the disease make more antibodies, health chiefs say.
It’s thought that antibodies in recovered patients’ blood can bolster the struggling immune system of infected people.
Hundreds of NHS Covid-19 patients are currently being treated with the blood of survivors as part of a national trial.
Analysis of donation shows 76 per cent of infected Brits who were hospitalised had high enough antibody levels for their blood to be used.
In comparison, fewer than a third of patients who weren’t whisked into hospital to fight the virus had enough of the disease-fighting proteins.
The NHS is now urgently calling for survivors who were left seriously ill to donate their blood, saying they could ‘save the lives of others’.
Convalescent plasma therapy is one Covid-19 treatment being tested in Britain, to see if it could help some of the sickest patients.
The treatment — first used in the 1918 Spanish flu pandemic and also given to treat SARS — works using the liquid part of the blood, known as convalescent plasma.
This antibody-rich plasma is injected into Covid-19 patients struggling to make their own antibodies, with hopes it can help clear the virus.
Antibodies are substances produced by the immune system which store memories of how to fight off a specific virus, such as SARS-CoV-2.
The data came from analysis of blood donations at 23 centres dotted around the country and a handful of pop-up sites.
Donating takes around 45 minutes and medics filter the blood through a machine to remove the plasma, in a process known as plasmapheresis.
NHS Blood and Transplant is now urgently appealing for donors ahead of a potential second wave.
Health chiefs are especially keen for donations from men, who have been found to make more Covid-19 antibodies than women.
People between the ages of 17 and 70 are welcome to donate, so long as they have big enough veins and enough blood to spare.
NHS Blood and Transplant’s Clinical Trials Unit is collaborating with the RECOVERY and REMAP-CAP trials on testing the therapy.
More than 13,000 donations have been taken, including more than 800 donations from people who were hospitalised.
There are 4,000 units of high antibody plasma units in stock and 1,500 have been issued to hospitals already. Around 190 people have received transfusions.
Dr Lise Estcourt, head of NHSBT’s Clinical Trials Unit, said ‘it is for people who were hospitalised with coronavirus to donate’.
She added that’ they are most likely to be able to save the lives of others seriously ill people’.
Dr Estcourt said the immune system produces more antibodies that neutralise or kill the virus in seriously-ill patients.
Former tennis player and TV presenter Dan Lobb donated his antibodies after a six-day stint in hospital fighting the virus.
He said: ‘It’s so new that they don’t yet know what truly works. That’s not a slight on the NHS.
‘The hard fact of this particular disease is there’s so little treatment available for them to turn to.
‘Donating plasma could be giving them a much needed weapon that could help save lives.’
Mr Lobb, 48, was hospitalised in April after his body began ‘shutting down’ and his oxygen levels dropped.
He said: ‘I couldn’t stand up due to nausea and dizziness. It got to the point when I couldn’t even sit up in bed.’
Mr Lobb added: ‘I ended up being one of the luckier ones who didn’t deteriorate and avoided treatment in ICU.
‘The staff did a fantastic job in difficult circumstances but it was clear there was relatively little they could offer to treat patients with Covid.
Injecting Covid-19 patients with the blood of survivors speeds up their recovery and reduces their symptoms, according to the latest study.
Researchers from the Karolinska Institutet in Sweden and Institute for Health and Welfare in Finland reviewed 10 studies looking into CP therapy.
Writing in the study, the academics said: ‘The results reviewed here suggest that CP therapy for COVID-19 is safe and effective.’
The scientists acknowledged that early results from China have shown the therapy has no effect on coronavirus patients, however.
Only dexamethasone has been proven to treat Covid-19 and thousands of patients worldwide are involved in trials of promising medicines.
A key advantage to the blood-based therapy is that it’s available immediately and relies only drawing blood from a former patient.
It is also significantly cheaper than developing a new drug, which costs millions to take through trials and regulation before mass production.