This winter’s Covid wave in the United States has been the gentlest to date, in a welcome reprieve.

According to wastewater data aggregated by the Centers for Disease Control and Prevention, not only was there less Covid circulating over the holidays than in previous years, but there was also less virus in the wastewater than in all the summer waves the program has tracked.

The Covid hospitalization rate stayed around half of what it was last year, and deaths fell too. In late December, around 600 people were dying each week. Last winter at that time, it was around 2,000. (During the Omicron surge at the end of 2021, weekly deaths were topping 10,000.)

Although wastewater levels can’t tell us how many individual cases of Covid there are, the recent data reflects a significant lull in the virus’s five-year assault.

“This is definitely the mildest Covid winter,” said Michael Mina, an epidemiologist and chief science officer for eMed. “In terms of hospitalizations, in terms of spread.”

A new low

One possible reason for the lull is that the population is still carrying some immunity from a large, later-than-usual summer surge, said Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco. This year’s vaccine was also a good match for the circulating variant, and more people got it this year than last, according to C.D.C. data.