What to Know: Breakthrough Infections
Breakthrough infections may be more common with the highly contagious Delta variant than with other versions of the virus. But the data are still unclear.
There is some evidence that people infected with the variant carry about 1,000-fold more virus in their bodies than those infected with previous variants, and may remain contagious for longer.
If that’s true even of vaccinated people, then some of them may be able to spread the virus to others.