Do COVID vaccines cause brain clots?

A new study is gaining attention from anti-vaccine groups because it calls for stopping COVID vaccinations worldwide. The study claims that brain clots are 1,120 times more likely after a COVID vaccine than after a flu shot and 207 times more likely than after all other vaccines combined.

This study should be viewed with extreme caution due to known issues with both the interpretation of COVID vaccine data and the potential misuse of the Vaccine Adverse Event Reporting System (VAERS) by anti-vaccine activists. Remember that anyone can report anything to VAERS, even if what they report wasn’t caused by the vaccine, as noted on the VAERS website. One doctor famously submitted a report that the flu shot turned him into the Incredible Hulk. VAERS is helpful for keeping track of vaccine safety, but just because something is reported doesn’t mean the vaccine caused it.

Claiming that brain clots are “112,000% more likely” or “20,700% more likely” after COVID-19 vaccination is misleading because the study uses Proportional Reporting Ratios (PPRs) that don’t account for the actual risk in the population. These ratios compare reported numbers without considering the context, such as the number of people vaccinated, heightened attention to COVID vaccine safety, and increased awareness about reporting adverse effects. In other words, the numbers alone don’t tell the whole story because they leave out these key pieces of background information.