To understand vaccine-induced immunity more fully, researchers are comparing antibody levels in people who received the Moderna vaccine but still got COVID-19 with levels in people who got the vaccine but didn’t fall ill.

A medical staff member prepares a syringe with a vial of the Moderna Covid-19 vaccine at a pop up vaccine clinic at the Jewish Community Center on April 16, 2021 in the Staten Island borough of New York City. (Photo by Angela Weiss / AFP) (Photo by ANGELA WEISS/AFP via Getty Images)