“He’s got a pass!” said the dad sitting across from me at the airport in Bismarck, North Dakota, where we were both stranded due to flight delays. He gestured to his 5-year-old son.“Had a slight fever and tested positive for COVID. We had to keep him home from school for a couple weeks. Then, he tested negative and was good to go. I got the vaccine. My wife did, too. But he can travel anywhere without any testing, and there’s no vaccine for his age anyway.”In Germany Natural Immunity CountsSince the beginning of July in Germany, where that family lives,...