This winter's U.S. COVID surge is fading fast, likely thanks to a 'wall' of immunity

Immunity Americans acquired through vaccination or via prior infection with the SARS-CoV-2 virus may account for the lighter than expected COVID surge in the U.S. this winter, researchers say. (David Ryder/Getty Images)

This winter's COVID-19 surge in the U.S. appears to be fading without hitting nearly as hard as many had feared.

"I think the worst of the winter resurgence is over," says Dr. David Rubin, who's been tracking the pandemic at the PolicyLab at Children's Hospital of Philadelphia.