AstraZeneca and Blood Clot Fears: What to Know About the Covid-19 Vaccine

More countries are limiting use of AstraZeneca's Covid-19 vaccine over blood clot concerns. The Netherlands joined a growing list of about a dozen places, including northern Italy and Ireland, moving to suspend the shot over concerns about possible side effects from two batches. While regulators from Europe to Asia said there was no indication of any direct link with the vaccine, reports of serious blood clotting after inoculation triggered a spate of suspensions stretching as far as Thailand.

The safety scare emerged against a backdrop of supply woes, and continue a drumbeat of bad news that started with questions about its initial trials and now extends to its potential faltering efficacy against a novel variant. Even as some countries suspend its use, others like the U.S. are moving to protect their own stockpiles, blocking efforts to redistribute the shot’s supply to places with urgent needs.

Astra has defended the vaccine, saying in a Sunday statement that more than 17 million doses have been administered in Europe and U.K., with no evidence that the shot increased the risk of blood clots. As of March 8, there have been 15 reports of clots in the legs, called deep vein thrombosis, and 22 cases where they reached the lungs, known as pulmonary embolism.

Politicians are acting with an abundance of caution, but run the risk of hurting global efforts to vaccinate, said Helen Petousis-Harris, a vaccine safety expert at the University of Auckland and a former World Health Organization adviser on vaccine safety.

“You have to be very careful because it’s also sending a message that there could be something very wrong with the vaccine when in fact, it’s very unlikely that there is,” she said. “We’re doing massive mass vaccination campaigns and people get sick all the time. We can’t panic every time it happens. But we also need to take all precaution. And it’s a hard balance.”

The number of events are lower than what would be expected to occur naturally in a general population of that size, AstraZeneca’s Chief Medical Officer Ann Taylor said. In studies, participants getting the vaccine had fewer clots than those given placebo.

On March 15, Thailand said it would resume its planned rollout of the shot this week, four days after suspending it, as a medical panel had decided that the vaccine did not lead to clots. Prime Minister Prayuth Chan-Ocha and some of his cabinet members will be receiving it on Tuesday.

The drama keeps Astra at the center of a political storm in Europe, weeks after manufacturing issues first put the two sides into conflict. Meanwhile, the EU is falling further behind the U.K. and the U.S. in vaccinations, creating a political crisis for the bloc’s leaders.

Even as some governments suspend dosing, they’re moving to protect their supply. Italy made use of a new EU measure to stop Astra from shipping some doses to Australia on March 4, and Prime Minister Mario Draghi hinted on Friday that he’ll do that again if he has to.

“The European Union has taken clear commitments with pharmaceutical companies and we expect they will be respected,” Draghi said. “We have taken some strong decisions against companies which have delayed the deliveries and we will continue to do so.”

The latest developments will do little to encourage take up of the Astra vaccine in the EU, which had already encountered issues in recent weeks in light of the varying efficacy rates, potential loss of protection against new virus variants, and questions on its effectiveness in older adults. Until recently, a number of countries had restricted use of the shot to those aged under 65.

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