But why doesn’t Johnson & Johnson appear to be as good at preventing mild illness?

There are a few possible answers. For one, Johnson & Johnson’s research trials seem to have had a greater degree of difficulty. They occurred later than Moderna’s or Pfizer’s — after one of the virus variants had spread more widely. The variant appears to cause a greater number of mild Covid cases among vaccinated people than the original virus.

Second, Johnson & Johnson is currently only one shot, while Moderna and Pfizer are two shots. That happened mostly because of how strong the Johnson & Johnson vaccine is. Initial testing showed it to deliver impressive levels of immunity after only one shot, while the others required a booster, as Dr. Robert Wachter, chair of the department of medicine at the University of California, San Francisco, explained to me…

“The number that we should all truly care about is what are the chances I’m going to get this thing and get really sick or die,” Wachter said. After any of the three vaccines, he added, “There’s essentially no chance you will die of Covid, which is breathtaking.”