The AstraZeneca Vaccine Blood-Clot Issue Won’t Go Away

But how far should this logic go? Does it matter that other COVID-19 vaccines are on the market—even if they’re more expensive or in short supply? Should vaccine authorities adjust their approach to risk, with the goal of propping up the public’s trust? These questions have no simple answers, and we shouldn’t be surprised that highly qualified experts have come to different conclusions.

In fact, we saw something like the same debate unfold late last year, when AstraZeneca and Oxford University first announced their vaccine’s success in clinical trials. The data contained numerous, serious shortfalls: Instead of judging efficacy from a single, large, placebo-controlled trial, the Oxford team merged results from different studies carried out in different ways. The research was so problematic, in fact, that regulators could not agree on whether the vaccine’s demonstrated efficacy against symptomatic COVID-19 was closer to 70 percent, as England’s drug regulator decided, or in the low 60s, per the EMA.

The lack of better data was a deal breaker for some health authorities. The U.S. Food and Drug Administration, for example, decided to await results from a large, rigorous trial; Switzerland’s agency, Swissmedic, did the same. But regulators in Europe, along with those in many countries beyond the Continent, went the other way. The EMA recommended authorization of the AstraZeneca vaccine, announcing that “the conduct of studies was sub-optimal” but also that, “given the emergency situation,” the benefits of using it outweighed any risks.

In this case, the choice to loosen up paid off: The vaccine has reduced disease and death in recent months, and the more rigorous clinical-trial results—which have only just come in—showed an efficacy of 76 percent. But that doesn’t tell us how regulators should handle the possibility of dangerous reactions to the same vaccine that are too rare to show up in a clinical trial, even one with 32,000 participants. And to some extent, the narrative about those reactions is no longer in their hands.

Stories linking people’s deaths to vaccinations have been among the most popular vaccine-related stories on social media in recent months—and that was true long before there were any hints of a real association. Now that health authorities really are investigating a possible, fatal vaccine reaction, these narratives will increase their reach. The first face to be linked prominently to the blood disorders appeared on Facebook on March 22. More seem sure to follow.

It may be that at some point soon a non-vaccine cause will be established, or treatments will render the condition manageable. Until that happens, though, regulators must do their best to maintain calm, perspective, and transparency. Imagine if they’d reacted more conservatively from the start, and waited to say or do anything until the number of people who turned up with this condition had reached into the hundreds. More people would have been vaccinated along the way, but the eventual loss of trust in the monitoring system for vaccines could have been far more severe. Addressing concerns about vaccines is a long game, and the biggest challenges will come much later on, when all the eager people have been immunized and it’s time to persuade the holdouts.

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