Europe's pause on the AstraZeneca COVID vaccine plays right into anti-vaxxers' hands

Last week, more than a dozen European countries suspended the AstraZeneca Covid-19 vaccine. They claimed it was out of an excess of caution, but instead they played right into the hands of those who continue to spread anti-vaccine misinformation.

On Thursday, the European Medicines Agency announced that there was nothing to worry about, that the AstraZeneca vaccine was safe, and that all countries should resume using it.

Too late, I fear. The harm has already been done.

I’ve been fighting the anti-vax movement for years, as have many other scientists, doctors, and science bloggers. We’ve seen their strategies, and they don’t play fair. They don’t care about facts, and they love to scare people. This latest incident gives them plenty of fodder.

First let’s talk about the “fear” part. A very, very small number of cases were reported in which people had blood clots soon after getting the vaccine. This sounds scary.

But wait a minute. We are giving the vaccine to millions of people. If you look at a group that large, how many of them will have blood clots in a given week? The answer, not surprisingly, is greater than zero.

So the first thing that public health authorities should have asked is, obviously, are we seeing more blood clots than expected? But no, they didn’t do that. Instead, out of an excess of caution (so they claimed), they halted the AstraZeneca vaccine while they investigated. This meant that literally millions of vaccine doses were not administered.

Fortunately the investigation took only a few days. What did they find? Well, here’s the answer, directly from the European Medicines Agency itself:

“the number of thromboembolic events reported after vaccination ... was lower than that expected in the general population.”

In other words, the vaccine clearly doesn’t cause blood clots. If anything, it might even prevent blood clots, because the number observed was lower than expected. (No one is claiming that it actually prevents blood clots; I’m just pointing out how wrong the decision to halt the vaccine was.)

Now the unfounded fear of vaccine-induced blood clots has spread through Europe and beyond. You can’t “unsay” something like this, and anti-vax websites and social media groups are already using it to scare more people. (I won’t link to any of them because I don’t want to give them the traffic.) Indeed, several northern European countries still haven’t resumed use of the vaccine, and Germany, France, and Italy are including a warning (an incorrect one) that the vaccine might cause blood clots. This is just wrong.

Halting the AstraZeneca vaccine without doing some very basic number-checking was a huge blunder. Let’s just hope this decision doesn’t cost too many lives.