Breakthrough infection

A breakthrough infection is an infection caused by the live virus in a vaccine or, simply, a vaccinated individual becoming sick with the same illness that the vaccine is meant to prevent. Often, the infection in the vaccinated individual is milder than if contracted naturally. A breakthrough infection can be especially dangerous in locations where herd immunity exists.

There are many theories which attempt to explain the causes of breakthrough infections such as antibody interference or vaccine compromise due to mishandling.