In a study published this week, Swedish researchers studied the risk of developing deep vein thrombosis or pulmonary embolism after contamination with the virus. This risk is present up to 6 months after an infection.
A SARS-CoV-2 infection is likely to have serious long-term consequences for the health of an infected person. According to a study published Wednesday, April 6 in the British medical journal (BMJ), Covid-19 increases the risk of developing serious blood clots for up to six months after infection. The Midi Dispatch takes stock of this new information.
What does this new study say?
It was already known that Covid-19 increased the risk of severe blood clots (known as venous thrombosis), but there was less information on how long this risk was increased and whether it varied during different epidemic waves.
This Swedish study provides new data on this subject. It reveals an increased risk of deep vein thrombosis (a blood clot in the leg) up to three months after infection with Covid-19,pulmonary embolism (a blood clot in the lungs) up to six months later and a bleeding event up to two months later.
Who are most at risk?
This risk is higher in patients with comorbidities and those with severe Covid-19. It was more marked during the first pandemic wave compared to the second and third waves, also underlines the study. According to the researchers, the increased risks observed during the first wave compared to the following two could be explained by the subsequent improvements in treatments and vaccination coverage in older patients.
Is infection more at risk than vaccination?
These risks of thrombosis are also known for vaccination against the virus. In a British study, published in August 2021 in the British medical journalresearchers say there is a “increased risk” to develop this side effect after receiving an injection of the anti-Covid vaccine, but that this risk was almost 200 times “lower than that associated with infection with SARS-CoV-2”.
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The scientists compared the medical data of 29 million people who received their first dose of Pfizer-BioNtech or Oxford-AstraZeneca.
What actions to take?
For the researchers, these results justify the taking of measures aimed at preventing thrombotic events (such as the administration of treatments which prevent the formation of a clot in the blood vessels), in particular for patients at high risk, and reinforce the importance of vaccination against Covid-19.
What was the method of the researchers?
To conduct their study, the researchers identified more than one million people in Sweden who were infected with SARS-Cov2 between February 1, 2020 and May 25, 2021, matched by age, sex and place of residence to more than four million people who had not tested positive for Covid.
They then calculated the rates of deep vein thrombosis, pulmonary embolism and bleeding in people who had Covid-19 during a control period and made comparisons with a control group.