Much more likely to develop thrombosis while flying than after injection with AstraZeneca, but that is not all

Internist Robin Peters said in Op1: “You are 100 times more likely to get thrombosis from a flight to Rhodes than from vaccination with AstraZeneca.” The chance of a form of thrombosis in an airplane is higher, but the comparison is complex.

Internist Peters made the comparison with flying to Rhodes mainly to indicate that the chance of getting thrombosis due to the AstraZeneca vaccine is very small. But is the statement true that the probability is 100 times greater? “It’s like comparing apples to oranges.”

Other cause

Because the thrombosis, the blood clot, which occurs in very rare cases after vaccination with AstraZeneca, has a completely different cause. “This is a special form that is caused by an excessive reaction by the immune system”, says Hugo ten Cate, internist vascular at the Maastricht University Medical Center.

This involves the formation of specific antibodies that react with parts of the blood clotting process. This causes the number of platelets to drop dramatically. Ten Cate: “It is an aggressive form of thrombosis that arises as a result, which is very specific.”

What is thrombosis?

With thrombosis, a blood vessel becomes blocked by a blood clot. If this clot breaks loose, it can lead to a bone thrombus, pulmonary embolism, or a heart or cerebral infarction if the clot obstructs an artery. Thrombosis is one of the main causes of death in the Netherlands. One in four people in the Netherlands dies from the direct or indirect consequences.

How about flying?

Sitting in an airplane for a long time increases the risk of thrombosis. Because sitting still for a long time in a cramped position in an airplane seat can lead to such a clot. Suzanne Cannegieter, professor of clinical epidemiology at the Leiden University Medical Center, investigated the likelihood of this happening among frequent air travelers on flights that last longer than 4 hours. “1 in 4,500 people who fly for more than 4 hours will develop a thrombosis,” she says.

To what extent is the statement of internist Peters correct at Op1? However, the journey from Amsterdam to Rhodes does not take 4 hours, but 3 hours and 40 minutes. Cannegieter estimates that the chance of thrombosis is then 1 in 5 to 6000.

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‘Nonsense comparison’

The rare but serious cases of thrombosis that led to the injection stop with AstraZeneca in the Netherlands are best documented in the United Kingdom. There, 20 million people have now received a vaccination from AstraZeneca. 79 people got the rare thrombosis variant. That means that the chance that you will get that rare form of thrombosis is 1 in 253,165.

If we assume a chance of 1 in 5,500 of contracting thrombosis on the plane, and you compare that with the chance of developing thrombosis after an injection with Astra Zeneca, then the chance is not 100, but 46 times as high as contract thrombosis during the flight Amsterdam-Rhodos. But, says Hugo ten Cate, a vascular internist at the Maastricht University Medical Center, then you compare apples with pears: “I think you should start juggling numbers like that. I think it’s a nonsense comparison.”

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