Is a spring coronavirus surge inevitable?

For the first time in months, there are reasons for optimism about the state of the coronavirus pandemic in the United States. The numbers of infections and deaths have dropped substantially from their peaks in the winter months. More than 50 million Americans have received at least one dose of the vaccine so far, and the vaccination rate is expected to increase. All this encouraging news has many experts predicting a return to a reasonable facsimile of normal by the summer.

A lot of those same experts, however, are warning...