There is an increased risk of a blood clot for the next six months after contracting Covid, according to new research.
People who had severe Covid symptoms, plus those who were infected within the first wave of the virus (before the vaccines) are most at risk, the Swedish study found.
Published in the British Medical Journal, the research said the risk of the blood clots was highest during the first wave of the pandemic.
It was lower during later waves due to better treatment of Covid plus the introduction of vaccines.
What did the research find?
The research included a large sample size of more than one million people in Sweden who had a positive Covid test between February 2020 and May 2021.
Researchers then compared them with four million people of the same age and sex who did not catch Covid.
In the first group, they found a heightened risk of blood clots in the leg, or deep vein thrombosis (DVT), for up to three months, blood clots in the lungs, or pulmonary embolism, for up to six months, and internal bleeding, such as a stroke, for up to two months.
Comparing the results to that of those who did not contract Covid, researchers found that four in every 10,000 Covid patients developed DVT compared with one in every 10,000 people who didn’t have Covid, about 17 in every 10,000 Covid patients had a blood clot in the lung compared with fewer than one in every 10,000 who did not have Covid.
Among those who were severely ill, the risk of a blood clot in the lung was found to be 290 times higher than normal, and seven times higher for those experiencing mild Covid symptoms.
For risk of internal bleeding, those with mild symptoms showed no raised risk.
Why is the risk higher?
Researchers can’t prove that it’s Covid that caused the blood clots but they have possible reasons why the risk is higher.
Some of the theories include the virus having an effect on the layer of cells lining blood vessels, it could be an exaggerated inflammatory response to the infection, or the body inappropriately making blood clots.
Should you be worried?
While it’s worrying to hear about blood clots, the risk is smaller for those with mild symptoms – which is the case now for many people since the introduction of the vaccine and booster programmes. And overall numbers are still low.
But for those who have not yet been jabbed, the research provides good reason to, say experts.
“For unvaccinated individuals, that’s a really good reason to get a vaccine - the risk is so much higher than the risk from vaccines,” Anne-Marie Fors Connolly, principal study investigator from Umea University in Sweden, told the BBC.
Can vaccinations cause blood clots too?
You’ll remember that one of the earlier vaccine suppliers, AstraZeneca, was shortly paused in countries around the world due to blood clot fears.
A study showed that some rare blood clots can appear after being vaccinated, but the risk was very small. The research also found that the risk of a blood clot after being infected with coronavirus was much higher.
So, if you’re not already, you might want to look into getting the jab.