For the last few weeks medical Twitter — and the more traditional media — has been full of risk management. The proximate cause has been the stories linking the Oxford/AstraZeneca vaccine, and then the Johnson and Johnson vaccine, to a tiny number of cases of a rare form of blood clots. The natural first reaction is to recoil. The second is to say, “Oh, come on, so few cases?” Then you remember that this time last year — the spring of 2021 is all about “this time last year” — a lot of people were saying the same thing about the coronavirus.
In the middle of these repeated revisions, Cambridge statistician David Spiegelhalter transformed the medical data on vaccine-related clotting cases and the impact of covid into an easy-to-grasp graphic that outlines the risk level for different age groups. A single glance is enough to explain the MHRA decision that this vaccine should not be offered to those under 30 — and enough to help anyone of any age see at a glance what the rational decision about getting the vaccine should be. In the age group 20-29, covid risk is substantially lower than the risk of vaccine-related blood clots based on the current data. In all other age groups, covid risk is substantially higher than the number who will be seriously harmed by the vaccine. (Though that is no comfort if you’re the friend or family of one of those people who is harmed.)
It’s a recurring theme among skeptics that humans are notoriously poor at assessing risk. For that reason, you’ll find that some of the same people who argued that covid’s fatality rate wasn’t significant enough to lockdown society to save lives … are now arguing that the 0.2 per 100,000 people aged 60-69 likely to experience serious harms due to the vaccine means it’s too dangerous to accept.
I suspect an important difference is that viral infection is something you avoid (if you can); taking a vaccine is something you do. Getting infected is bad luck; getting a serious illness or dying after being vaccinated means we made a bad decision. This perception remains true, I think, even if we got infected because we were stupid (hung out indoors with 100 drunks singing football songs with no social distancing or masks, all the windows closed, and no airflow) and the vaccination side effect was a one in a million chance that had never been reported before.
A day or two later, the US suspended the use of the one-shot Johnson and Johnson vaccine because of similar problems. “Six cases out of 7 million shots,” a friend commented, marveling at the decision to halt its use. You can see his point. And yet: “An abundance of caution.”
There are three reasons why this is a rational decision for the FDA to take: medical, social, and legal.
The legal issue is, of course, the US’s character as a highly litigious society. If the families of the six cases to date were to sue, the FDA and J&J could reasonably argue that emergency authorisation to use the vaccine was necessary in light of the ongoing crisis, and that no one knew the clotting problem would emerge. If the FDA did nothing and shots kept going ahead without any pause for thought, the next six cases could argue they were recklessly negligent.
The medical issue is that where there are six cases there may well be more that haven’t been recognised or counted yet. Now that these six cases have come to light and been publicised, health authorities everywhere will be looking to see whether there are other cases that have so far been overlooked. The likelihood is that they will find at least a few. In addition, because the J&J vaccine has only been in use for a month and rollout has accelerated rapidly during that time and cases take one to two weeks to develop, it is also likely that there will be new cases emerging in the next week. By the time they finish counting, there will very likely be more than six, and risk estimates will have to be revised.
The social issue is the most crucial one. Trust is a crucial aspect of public health. Many parts of the US — and some parts of the UK — are on a knife edge over whether people will actually take the vaccine, for numerous reasons. Some are hesitant for historical reasons; white doctors’ experiments on black and brown people have a notorious and shameful history. Others are dubious simply because of the short time frame in which the vaccines have been developed and distributed. This is especially true of the “new mRNA vaccines” styling, which has sent the message that these have been slapped together at the last minute on a wing and a prayer rather than the result 20 years of painstaking research that just luckily happened to be ready when the coronavirus hit. Others, for one reason or another, are militantly against all vaccinations. There’s little you can do about the last group, but the first two are vastly larger, and for them trust is crucial. Pausing the vaccine rollout has a high cost in infections and human lives, but it builds trust that the authorities are paying attention to the data and acting swiftly to ensure safety. In the long term, that trust should save more lives than the pause will cost.
*You can see it at https://twitter.com/stokel/status/1379805178623299585/photo/1
