What I find interesting in the replies to your comment is that you are not taken at your word. I find we have lost our ability to do that.
You’re point is a strong one: shortly after preforming a very novel and rare action, your sister got ill with a rare disease. Her Dr. also mentioned that he had seen multiple patients who shortly after preforming a novel and novel action they got ill with a rare disease.
instead the replies boil down to:
1. Correlation doesn't imply causation
2. its psychosomatic.
Both annoy me.
1. People forget that the inverse is also true - causation doesn't imply correlation. For example, a quadratic relationship between independent and dependent variable will show zero correlation.
So why bother with correlation at all?
Because we need something to tell us where to start looking
Take the famous ice cream sales vs. robberies example. A lot is learned explaining the strong correlation between the two, even though there is no causation.
Of course, all the AI fanboys have no problem with flaky correlation as long as they predict well and they don't have to explain them.
2. This one really annoys me. While I believe that psychosomatic reactions are real and understudied (my great uncle - head Dr. at the largest hospital in a large city once told my dad that half of all ailments are cured with placeboes) this explanation is far less mechanistic and unscientific than blaming the vaccine itself.
The explanation boils down to “i don't want to believe its something I cherish, so Ill blame your hysterical sister instead”.
Psychosomatic digestive, blood pressure and heart problems are hardly surprising. All those systems are tightly connected and controlled by the mind. But vein issues? What is the mechanistic link between the mind and veins?