AstraZeneca vaccine linked to rare blood clots, EU regulators conclude - Ars Technica

European medical regulators on Wednesday concluded that there is a strong link between AstraZeneca’s COVID-19 vaccine and life-threatening conditions involving the unusual combination of blood clots and low levels of blood platelets.

The conclusion was based on the EMA’s in-depth review of 86 blood-clotting events among around 25 million people vaccinated with the AstraZeneca vaccine in Europe and the UK.

Oddly, the clotting events have been accompanied by low levels of blood platelets, which are the blood cell fragments that stick together to form clots.

Some researchers suspect that the blood-clotting events linked to AstraZeneca’s vaccine may also be down to a similar berserk immune response, and it may be treatable.

As seen in people who develop HIT after heparin, the blood-clotting events and low platelets seen in vaccinees usually develop within two weeks of getting their first dose.

“The reported combination of blood clots and low blood platelets is very rare,” the agency noted, “and the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects.”.

The conclusion follows weeks of drama around the vaccine, in which more than a dozen countries that had already authorized the vaccine’s use abruptly halted vaccinations out of concern for the blood clots—then resumed use out of concerns for the spread of COVID-19.

And on Tuesday, the University of Oxford, which co-developed the vaccine with AstraZeneca, said that it had paused a small UK trial of the vaccine in children and teenagers.

In the latest misstep, the company got into a highly unusual and concerning spat with a panel of US experts tasked with overseeing its COVID-19 vaccine trial and data.

And it’s also likely to cast a shadow over the Johnson & Johnson COVID-19 vaccine, which is authorized in the US and elsewhere and uses the same design as AstraZeneca’s vaccine.

Still, the side effects seen in AstraZeneca’s vaccine raise worries about Johnson & Johnson’s.

During the clinical trials of the Johnson & Johnson vaccine, there was an early sign of an increased risk of these blood-clotting conditions in vaccinated people, Peter Arlett, head of data analytics at the EMA, said in a press briefing Wednesday.

Of the approximately 4.5 million people who have received the Johnson & Johnson vaccine worldwide, there have been three reported cases of blood-clotting events similar to those seen in people given the AstraZeneca vaccine, Arlett said.