That doesn't mean the vaccine caused all of those events.
The same principle applies to almost every medical treatment.
Scientists therefore use several methods to investigate possible adverse reactions.
One approach is to compare the number of cases observed after vaccination with the number that would normally be expected in a population of similar size and demographic characteristics.
Researchers can also compare vaccinated and unvaccinated groups, examine medical records, analyze patterns over time, and investigate biological mechanisms.
If a condition occurs at a rate significantly above the expected background rate, researchers investigate further.
This is how genuine safety signals can emerge.
Importantly, a reported adverse event is not necessarily a confirmed vaccine injury.
When a doctor, patient, or health system reports an illness following vaccination, the report may simply indicate that the event occurred after vaccination. It does not automatically establish causation.
This distinction is sometimes lost on social media.
A post may say:
"Person receives vaccine. Person later develops condition. Therefore, vaccine caused condition."
That conclusion skips several essential steps.
It is also why photographs are particularly dangerous when removed from their original medical context.
An X-ray might belong to a patient with a completely unrelated disease. The original case could have involved symptoms that existed before vaccination, another medication, an underlying condition, or a diagnosis unrelated to COVID-19 vaccination.
Without the patient's clinical history, laboratory results, imaging report, diagnosis, and medical assessment, strangers online cannot reliably determine the cause.
That doesn't mean every vaccine-safety concern should be ignored.
Quite the opposite.
It means legitimate concerns deserve better evidence, not weaker evidence.
A serious medical claim should be evaluated using clinical studies, surveillance data, and expert assessment rather than a frightening image and an unfinished headline.