Having the virus, you potentially could pass it on. A person with the vaccine can potentially expose someone else to sickness and death.
As far as sampling bias. a person with side effects is more likely to post about them then someone (like me) that has had no side effects of any kind from the vaccine. That makes it seem that side effects are more prevalent then actually exist.
Real statistics are tracked and the results are clear that the vaccine has significantly less risk of any kind compared to the actual virus.