The C.D.C. cannot know the nuances of every situation. So it’s no wonder that when it issues detailed advice, it often winds up confusing people instead of comforting them. The C.D.C.’s recent change in policy on masks for those who are vaccinated is a good case in point. In an effort to attempt to address every possible scenario, the agency published a pretty complicated document that tried to tell people whether they needed to mask in a wide variety of situations. Instead, it could have said this: When you’re vaccinated, your personal risk is substantially lower than ever before. You are significantly less likely to be infected. You’re much less likely to get sick in the unlikely event that you are infected. You’re even less likely to spread infection. Given that, masks likely provide limited benefit in most settings, so you really don’t need to wear one.