What does success look like for the Covid-19 vaccine effort?

Administration of Pfizer-BioNTech’s Covid-19 vaccine officially began on Monday. It was a joyous kickoff to a massive, arduous effort to vaccinate over 100 million Americans. But how will we know if the vaccination effort is actually going according to plan?

STAT posed that question to a handful of experts in the fields of public health, emergency preparedness, and bioethics. From our conversations, one thing was clear: Judging the success of a mass vaccination campaign is not as simple as making sure the number of people being vaccinated keeps on increasing. Here are a few answers that stood out to us.