Except the risk is not 0 if you don't have comorbidities.

People keep throwing this statement out as though somehow the risk of vaccination is higher then the risks due to viral infection. It is not.

The risks of adverse reactions to COVID infection is reduced across the board if you are fully vaccinated regardless of your health status.

Also worth noting: plenty of young people have comorbidities they don't know about yet, because they haven't found them. It is actually quite difficult to exclude yourself from the "has comorbidities" risk group apriori. A common one is in fact undiscovered heart conditions for people in their 30s, since they usually only become an issue later in life when symptoms are more likely to present.