Thanks for your thoughtful comment. I think the adverse events are deemed unrelated to the vaccine if the attending physician thinks the adverse event would have occurred even without vaccination.

The small cases of cancer progression, for example, are something that can occur from the nature of cancer itself. (But the lack of data in the control group prevents this confirmation).

An adverse event is deemed related to the vaccine if there is no other apparent cause. For example, we know vaccine-induced thrombotic thrombocytopenia (VITT) is caused by the vaccine because such a condition has never happened before. We also know vaccines can cause myocarditis because of the increase in myocarditis rates in the vaccinated compared to unvaccinated group across multiple studies and countries.

I hope I answered your question but just let me know if anything is unclear.