Why European vaccine suspensions could have unintended consequences

Europe’s difficult rollout of covid-19 shots took another blow over the weekend, as several countries halted deployment of the AstraZeneca vaccine amid worries it could cause blood clots.

On Monday Germany, Spain, Italy, and France were among those to suspend deployment of the vaccine, following similar moves made last week by Denmark, Norway, Ireland, and others. Germany’s health minister, Jens Spahn, said it was “a purely precautionary measure” after some reports that a small number of people who had received the vaccine later developed blood clots in their brains.

The European Medicines Agency, meanwhile, said that although there have been around 30 reports of clotting among 5 million people vaccinated, this was not higher than the incidence that would normally be expected. In an announcement on Monday, it said that the vaccine can still be delivered while further investigations take place.

“Events involving blood clots, some with unusual features such as low numbers of platelets, have occurred in a very small number of people who received the vaccine,” the agency said in a statement. “Many thousands of people develop blood clots annually in the EU for different reasons. The number of thromboembolic events overall in vaccinated people seems not to be higher than that seen in the general population.”

Meanwhile, the health-care regulator in Britain—which has delivered 11 million shots of the AstraZeneca vaccine so far, many more than any other country—says there’s no evidence that this vaccine presents a heightened health risk.

But conflicting messages about how serious these reports are—and therefore how risky the vaccine is—have left people worried and confused about what’s going on. Some experts are concerned that the news may damage wider efforts to get people inoculated against the coronavirus.

“We haven’t got much to go on, because governments are putting out statements, but they are not really putting out data,” says Michael Head, a senior research fellow in global health at the University of Southampton in the UK. “Germany seems to have seen a very slightly elevated risk of thrombosis … but I’m just not seeing any data that suggests we should pause rollout.”

One factor in the suspensions, he suggested, may be that Europe is currently still in the earlier stages of vaccination rollout—meaning that some of those receiving doses at the moment are among the most frail or at the highest risk for medical problems. AstraZeneca says its own studies show that clotting incidents are lower than would be expected among the general population.

The situation also plays into a broader narrative about vaccination risk. Many European countries have high levels of vaccine hesitancy—one study in France suggested that only 40% of people were planning to get vaccinated against covid-19—and the AstraZeneca vaccine, in particular, has sparked more concern and speculation than others.

Germany and France did not initially approve this vaccine for people over 65, and after South Africa halted rollout when data suggested it was less successful against the local variant of the disease, it became unpopular in some European countries.

The US has yet to approve the AstraZeneca vaccine, despite giving emergency authorization to three other rival products, and is waiting for further trial results. As part of Washington’s race to get enough vaccines into production, however, the government did place an order—which means there is now a stockpile of some 30 million doses.

The suspensions, so far, are extremely short: France’s regulator says it will issue new guidance on Tuesday.

“Countries are being overly cautious, and there will be consequences,” says Head. “Pausing vaccinations means doses aren’t going into people’s arms. Plus, there’s public confidence: Will this pause increase hesitancy? Will this stick in the public consciousness? It’s become a bit of a political football.”

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