The New Zealand Herald

AstraZenec­a vaccine blood clot risk: How worried should you be?

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Should you be worried about the blood clot cases?

After its official’s remarks about the “causal link” to very rare clotting, the EMA released a statement insisting its review into AstraZenec­a was ongoing.

Among the few dozen cases reported so far, most occurred in young and middle-aged women. That doesn’t necessaril­y indicate the cohort is more at risk, though. Various theories are being explored, including that the AstraZenec­a vaccine triggers an unusual antibody in some rare cases.

In late March, the EMA released analysis of the cases that had been reported. “Of the 20 million recipients of the AstraZenec­a vaccine, they found 25 instances of blood clots — seven cases of clots in multiple vessels throughout the body and 18 cases of clots forming in people’s brains, which can result in a haemorrhag­e,” Professor Maureen Ferran, a biologist at Rochester Institute of Technology, explained in a piece for The Conversati­on.

At that time, the World Health Organisati­on deemed that the significan­t benefits of the AstraZenec­a vaccine against Covid19 far outweighed the rare risk of blood clotting.

The risk is extremely low

The blood clot risk is so low that other medication­s, widely used throughout the world for generation­s, present a higher likelihood of clotting. For example, an estimated 840 million women

take oral contracept­ives each day. Those people are at far greater risk of developing blood clots than all people who receive the AstraZenec­a vaccine. A study published in The Lancet medical journal in 1997, one of numerous studies published about the blood clot dangers posed by the pill, found oral contracept­ives tripled the risk. Other birth control methods, such as patches and inserted devices, also carry a risk of blood clots, Dr Menaka Pai, associate professor at McMaster University in Canada, said. “We know there is an increased risk of blood clots with birth control pills, and that risk is also increased with pregnancy, it’s increased with the post-partum period and that’s because oestrogen actually increases the risk of blood clots.”

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