A co-worker of mine here in California told me about a friend of his, Dave, who never got the COVID shot but, in late December 2021, got COVID. In his early 50s, remarkably fit, with no comorbidities, and with Christmas just a couple of days away, he figured he could ride out the virus at home. But he only got worse, ending up with symptoms so severe that his wife, fearful for his health, insisted that he go to the hospital after Christmas. With his lungs failing, Dave was put on a ventilator. But once the machine took over his...