Somehow, though, the “insufficient data” problem disappeared when it came to lockdowns and mask mandates. Before the pandemic, the official expert consensus was against those measures, but the consensus was promptly discarded in the hope that these sacrifices might help. The evidence since then could easily be called insufficient, given the lack of randomized studies and the inconvenient data showing that places with lockdowns didn’t fare any better than the places without strict measures. And given what has emerged about the minuscule rate of transmission in outdoor settings, you could certainly say there’s insufficient evidence to order people to stay inside their homes or to mandate masks outdoors.

But whatever these lockdowns and mandates do or don’t accomplish in stopping viral spread, they definitely enable officials and citizens to demonstrate that they’re taking bold actions against Covid—and the more painful the measures, the more virtuous and heroic they feel. Whenever evidence emerges that the lockdowns are ineffective, the proponents have a ready answer: not enough people are following the rules. Stop sinning! Do your penance!

Going out for a walk or taking a vitamin D pill is just too easy. It entails no pain and provides no glory or power to public-health officials and politicians, so they rarely give this advice despite the evidence that vitamin D helps the immune system against viral infections. It’s not surprising that groups with disproportionately high rates of Covid mortality are also prone to vitamin D deficiency: African-Americans and other minorities, the obese, residents of nursing homes and other elderly people. Levels of vitamin D tend to decline with age, and because the vitamin is synthesized in the body by exposure to sunlight, people tend to have lower levels if they spend less time outdoors or have darker skin that absorbs less ultraviolet radiation from the sun.