Prior to COVID more than 300 million people travel on long-distance flights (generally more than four hours) each year.1 Blood clots, also called deep vein thrombosis (DVT), were already a serious risk for some long-distance travelers.
Travelers have never been more aware of their health and safety when flying. But for some people, the novel coronavirus isn’t the only health risk they’re worried about on airplanes. The CDC and airline industry are yet to address the risk of COVID, vaccines and the safety of flying after infection or vaccination.
According to the National Blood Clot Alliance, an average of 274 people die from blood clots every day and 600,000 nonfatal blood clots occur every year. Air travel can increase this risk as you’re sitting for long periods with little room to move your legs. This can cause a particular type of blood clot called deep vein thrombosis (DVT).
Among the many mysteries is exactly how SARS-CoV-2, which is the novel coronavirus that causes COVID-19, triggers the formation of blood clots that can lead to strokes and other life-threatening complications, even in younger people.
On 13 April, US regulators urged health-care providers to temporarily stop using a vaccine made by Johnson & Johnson (J&J) of New Brunswick, New Jersey, because of six suspected cases of unusual blood clotting among nearly seven million vaccine recipients.
COVID-19 can make blood cells more likely to clump up and form clots. While large clots can cause heart attacks and strokes, much of the heart damage caused by COVID-19 is believed to stem from very small clots that block tiny blood vessels (capillaries) in the heart muscle.
The chance of developing cerebral venous sinus thrombosis was nearly 10 times higher in the two weeks following a diagnosis of SARS-CoV-2 infection than after receiving an mRNA vaccine, a data analysis finds. The level of risk from an extremely rare form of blood clot being investigated as possible link with the Oxford/AstraZeneca vaccine is at the same as taking a long-haul flight.
Most information about blood clots and long-distance travel comes from information that has been gathered about air travel. However, anyone traveling more than four hours, whether by air, car, bus, or train, can be at risk for blood clots.
Symptoms of a blood clot
Knowing you have a blood clot can be tricky, as you can often write off the symptoms as something else, but there are a few key warning signs to pay attention to when traveling. If you experience these symptoms, you should seek medical help immediately.
“If you develop pain, tenderness, swelling, warmth and/or redness in your legs during a flight, those may be signs of a deep vein thrombosis or blood clot,” said Dr. Favini. “If you have more than one or many of those symptoms, it becomes more likely that you’re experiencing a clot.”