The United States reached a major milestone this week, with the White House reporting that over half of all adults in the U.S. are now fully vaccinated against COVID-19.

This announcement came on the same day as a new report from the Centers for Disease Control and Prevention that breakthrough COVID-19 infections are exceedingly rare in fully vaccinated people.

A breakthrough infection is when a fully vaccinated person becomes infected with COVID-19.

The new CDC report shows that such breakthrough infections may occur in just 0.01% of all fully vaccinated people.

Vaccines are highly effective at preventing infection, but none are 100% protective. Even when these rare breakthroughs happen, the vaccines are still overwhelmingly effective at protecting people from being hospitalized or dying.