The biggest reason for this improvement is that virtually everyone in the United States has some form of immunity now, whether from vaccines, a previous infection or both. Medications like Paxlovid have also significantly reduced the risk of serious illness.

Dr. Taison Bell, an infectious disease physician at the University of Virginia, said that in his intensive care unit, “we will see an occasional Covid-19 case, but we’re not seeing a lot of cases that are leading to people being on the ventilator.” Now, most of the people Dr. Bell is treating for Covid are older and either have pre-existing conditions that compromise their immune systems or lung function, or they haven’t been vaccinated. It’s essential, he said, that people who are at high risk for severe infection get a bivalent booster if they haven’t already (a second dose was also recently authorized for this group).

Another reason things are different this spring is that there have been no new, game-changing variants — “no new Greek letters,” as Dr. Wachter put it — for the last year and a half. Variations of Omicron that have some immune-evading properties, such as the current dominant strain, XBB.1.5, have emerged, but Paxlovid and vaccines are still effective against them.

Despite the good news, experts are still taking some precautions. Because while the numbers are headed in the right direction, roughly 100,000 Americans are still being infected with Covid-19 every week, and more than 150 are dying from the infection every day.

Dr. Wachter continues to wear a mask in most crowded indoor settings, like on an airplane or in a museum, he said, but not if he needs to pop into a store quickly.