My older siblings and I all had the mumps, measles, rubella, chickenpox and whooping cough, and, apart from the whooping cough, neither we nor our parents remember us being seriously ill. Nonetheless, we all had all the vaccines offered, which is why younger siblings did not get all of the ‘childhood illnesses’. We were lucky.
All my children are fully vaccinated. I know two young adults who caught one of these illnesses when younger, despite being fully vaccinated, and who developed life-threatening, life-changing auto-immune disorders within weeks of recovering. One now lives with T1 diabetes, the other with Crohns. They were 100% healthy before, and have no family history of either condition.