...except common sense isn't so common. You and I may have it, but the idoit baby factory down the street, not so much. You want to sit next to him/her on a plane, with your kid, who's too young to be vaccinated? Or any other number of ways your kid can come in contact with him/her or their ilk? Most common sense laws are for idiots with no common sense. Think seatbelts, texting while driving... making parents immunize their cute little bundle of snotty virus incubator.
Were not speculating here. The vaccines we're talking about all but eradicated the measles virus from the western hemisphere, except for those pesky asshats who insist on not vaccinating and traveling, willy nilly, to places around the world, where the disease is still prevalent, and then traveling back home, infected. Common sense?
I do however, wholeheartedly agree with, and subscribe to your statement on vitamins and hand washing. Excellent preventive maintenance.