Vaccinated People May Spread the Virus, Though Rarely, C.D.C. Reports

In yet another unexpected and unwelcome twist in the pandemic, fully immunized people with so-called breakthrough infections of the Delta variant may spread the virus to others just as easily as unvaccinated people, the Centers for Disease Control and Prevention said in a report published on Friday.

The vaccines remain powerfully effective against severe illness and death, and infections in vaccinated people are thought to be comparatively rare. But the revelation follows a series of other findings this week about the Delta variant, all of which have upended scientists’ understanding of the...