The summer of 2021 is shaping up to be historic.

After months of soaring deaths and infections, COVID-19 cases across the United States are declining even more sharply than experts anticipated. This is expected to continue, and rates of serious illness and death will plummet even faster than cases, as high-risk populations are vaccinated. Even academics who have spent the pandemic delivering ominous warnings have shifted their tone to cautiously optimistic now that vaccination rates are exploding.

Until very recently, Anthony Fauci had been citing August as the month by which the U.S. could vaccinate 70 to 80 percent of the population and reach herd immunity. Last week, he suddenly threw out May or early June as a window for when most Americans could have access to vaccines. Despite some concerns about new coronavirus variants, Ashish Jha, the dean of the Brown University School of Public Health, told me he doesn’t see viral mutation as reason to expect that most people couldn’t be well protected within that time frame.