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Blood-thinning drugs have been linked to a reduced risk of death among people hospitalised with the coronavirus.
Early in the pandemic, reports emerged the infection can make blood stickier in severe cases, prompting patients to endure strokes and even gangrenous limbs.
While three coronavirus vaccines are approved in the UK, no jab is completely effective. Some individuals, like cancer patients, are also not always well enough to be immunised, highlighting the continued need for effective treatments.
To learn more, scientists in the UK and US administered anti-clotting therapies to more than 3,600 patients within a day of them being admitted to hospital with COVID-19, the disease caused by the coronavirus.
Results suggest these patients were over a third (34%) less likely to die than the individuals just treated with the standard of care.
Early research suggests the coronavirus is mild in four out of five cases.
Nevertheless, COVID deaths have been attributed to blood clots that travel from the deep veins in the legs, arms or groin to the lungs, where they become lodged.
Clots in the arteries can also obstruct or block blood flow to major organs like the heart or brain, which can have life-threatening consequences.
Several organisations, including the American Society of Hematology, have therefore suggested blood-thinning drugs be given as a preventative treatment when patients are hospitalised with the coronavirus.
Watch: How is severe coronavirus treated?
With only small studies being carried out beforehand, the scientists looked at more than 4,200 adults who were admitted to hospital with a confirmed coronavirus infection between 1 March and 31 July 2020.
The participants had an average age of 68 and more than nine in 10 (93%) were male. Statistics have repeatedly flagged men are significantly more likely to become seriously ill with the coronavirus.
Of the more than 4,200 adults, over 3,600 were given preventative blood thinners within 24 hours of their admission. These patients were compared against 670 others who received the standard of care alone.
Nearly all (more than 99%) of the patients who received blood thinners were injected with the drugs heparin or enoxaparin.
Of these, 14.3% died within 30 days, compared to 18.7% of those in the standard of care group.
The results, published in The BMJ, suggest administering blood thinners reduced the patients' death risk by up to 34%.
These findings remained true after the scientists adjusted for the participants' age, ethnicity, underlying health, weight and smoking status; all of which can influence the onset of coronavirus complications.
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As well as preventing blood clots, anticoagulants may also "possess antiviral and potentially anti-inflammatory properties", which could be particularly beneficial for coronavirus patients, wrote the scientists.
Research has shown the sickest coronavirus patients have a substantial amount of inflammation in their lungs, which may come about if their immune system goes into overdrive after encountering the infection.
Administering blood thinners raises the risk of dangerous bleeding, however, this did not occur in the study. Individuals who had been prescribed anticoagulants in the past could not take part in the trial.
The scientists – led by the London School of Hygiene & Tropical Medicine – acknowledged their study was observational, and therefore does not prove cause and effect.
Nevertheless, the team has said their results "provide strong real world evidence to support guidelines recommending the use of prophylactic anticoagulation as initial treatment for patients with COVID-19 on hospital admission".
With further research being required, Dr Mark Skidmore from Keele University added: "Different heparin treatment regimes are available – IV [intravenous], SC [subcutanous; injected beneath the skin], nebulised [inhaling a drug as a fine spray] – each of which may be targeting a specific disease status, and these need testing.
"While vaccines are becoming a reality, the emergence of variants of concern where vaccine protection may be drastically reduced, available therapeutics of proven efficacy become even more important.
"Here, it is important to recall heparin is already widely used and available, while being a relatively cheap drug with a strong safety track record."