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07th Apr 2022

People who have Covid in the last six months warned over blood clot risks

Charlie Herbert

Blood clots covid risk

People with underlying health conditions and who had more severe symptoms are most at risk

A new study has found that people who catch covid are at a increased risk of developing blood clots for six months after they were infected.

In the 30 days after infection, the research found that there was a 33-fold increase in the risk of developing a pulmonary embolism, which is a blocked blood vessel in the lungs.

Researchers also found that the risk of deep vein thrombosis (DVT) was “significantly increased” for three months after catching the virus, and that there is a greater chance of a “bleeding event” in the two months after being ill.

Although research had already suggested that catching covid increased a person’s risk of developing blood clots, researchers at Umea University in Sweden wanted to establish how long this risk lasted for.

The findings, published in the British Medical Journal, said that even mild non-hospitalised covid sufferers are at risk of these side effects, but that those with underlying health conditions are most at risk along with people who experienced more severe symptoms.

However, the risk of these blood clots decreased in the second and third waves of the pandemic, which researchers said is likely to reflect the development of vaccines and treatments, particularly for the elderly.

Anne-Marie Fors Connolly and her colleagues looked at data from more than a million people who caught covid between February 2020 and May 2021, and compared this with more than four million people who didn’t have the virus.

They found a five-fold increase in the risk of DVT and a 33-fold increase in the risk of pulmonary embolism and an almost twofold increase in the risk of bleeding in the 30 days after infection amongst those who caught covid.

People remained at increased risk of pulmonary embolism for six months after becoming infected, and for two and three months for bleeding and DVT.

They concluded: “Our findings arguably support thromboprophylaxis to avoid thrombotic events, especially for high risk patients, and strengthen the importance of vaccination against Covid-19.”

In an editorial addressing the research, Dr Frederick Ho, a lecturer in public health at the University of Glasgow, said that the results show we must “remain vigilant” about the continued risks of covid-19.

He said: “Despite the potential for new variants of concern, most governments are removing restrictions and shifting their focus to determining how best to live with Covid.

“This study reminds us of the need to remain vigilant to the complications associated with even mild Sars-CoV-2 infection, including [blood clots].”

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