Reports of rare vaccine breakthrough infections show how well the vaccines work. CDC reports findings of <1/14,000. Ongoing evaluation will help develop future versions of the vaccine to respond to the variants.

Medical Mythbusting Commentary for April , 2021

Source:
Only 2 “breakthrough” infections among hundreds of fully vaccinated people, new study finds
So far, 5,800 fully vaccinated people have caught Covid anyway in US, CDC says

Reference:
Vaccine Breakthrough Infections with SARS-CoV-2 Variants