Understanding one in 100,000

What does this tiny probability look like?

The EMA stated there was a plausible link between the Oxford-AstraZeneca (Vaxzevria) vaccine and rare blood clots. The European Medicines Agency said the probability of this kind of blood clot was “very low”. With millions vaccinated, very rare side effects can emerge.

The Paul-Ehrlich-Institut reported brain blood clots with low platelets in one in 100,000 vaccinations. The MHRA figure was a little lower: at about 0.4 in 100,000. The disparity comes from coverage, case definition…