COVID-19 survivors may have an increased risk of blood clots or strokes, study says

Serious complications due to blood clots, such as heart attacks and strokes, that are experienced by some novel coronavirus (COVID-19) survivors may be caused by a lingering immune response in the blood vessels after recovery, according to a new study published in the journal eLife.

For the study, researchers collected blood samples from COVID-19 survivors within a month of their recovery and discharge from the hospital. The researchers found that, in comparison with healthy individuals, COVID-19 survivors have twice as many damaged blood vessel cells, called circulating endothelial cells, floating in their blood. Even more of these damaged blood vessel cells were found in survivors who had conditions such as hypertension or diabetes that can also damage the blood vessels.

In addition to signs of blood vessel damage, the team found that survivors had an abundance of inflammatory proteins called cytokines that are produced by immune cells. They also found unusually high numbers of immune cells called T cells, which help destroy viruses, despite the fact that the virus was already gone, according to the study.

The findings may help explain why some COVID-19 survivors, so-called “long-haulers,” report lasting COVID-19 symptoms or why some experience strokes or heart attacks weeks or months after recovery. They may also suggest potential strategies to help prevent these complications, the researchers said.

"Our work suggests that COVID-19 patients, especially those with underlying chronic conditions, may benefit from close post-recovery monitoring," said Christine Cheung, PhD, senior author of the study and assistant professor at the Lee Kong Chian School of Medicine in Singapore, in a statement. "This would help identify high-risk individuals who may need blood thinners or preventative therapy to protect them from debilitating blood-clotting complications."

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