https://apnews.com/8da12b3d4f6e33c0c6562f29f81ca52a

Health officials around the world are racing to vaccinate enough people to stop the spread of COVID-19, but what qualifies as “enough” is still an open question.

The goal is to get to “herd immunity,” which is when enough people have immunity, either from vaccination or a past infection, to stop uncontrolled spread.