So when the European Medicines Agency says there have been 30 “thromboembolic events” after around 5m vaccinations, the crucial question to ask is: how many would be expected anyway, in the normal run of things?
We can try a quick back-of-the-envelope calculation. Deep vein thromboses (DVTs) happen to around one person per 1,000 each year, and probably more in the older population being vaccinated. Working on the basis of these figures, out of 5 million people getting vaccinated, we would expect significantly more than 5,000 DVTs a year, or at least 100 every week. So it is not at all surprising that there have been 30 reports.