Context also matters. About one in 10 Americans have reported an allergic reaction to penicillins. About one in 100, perhaps, have a true allergy to that class of drugs (I’m one of them). Between one in 2,500 and one in 5,000 experience anaphylaxis. But pediatricians like me dispense penicillin all the time, with minimal concerns. We do so because most allergic reactions are minor and serious ones can be managed, and because we believe that the benefits outweigh the harms.

Every potential bad outcome of a Covid vaccine should be weighed against the chance of getting sick or dying from the disease.

Using data from Indiana, which has conducted multiple statewide studies on the prevalence of Covid-19, colleagues from the I.U.P.U.I. Fairbanks School of Public Health and I calculated the disease’s infection fatality rate. We found that, for people 60 years and older who were not living in jails or nursing homes, Covid-19 killed about one in 58 of those infected. For people between the ages of 40 and 59, it was about one in 833, and for people younger than 40 it was about one in 10,000. For those who were not white, the fatality rate was more than three times that for whites.