These data, gathered from blood donors, represent estimates of the percent of the U.S. population ages 16 and older that have developed antibodies against SARS-CoV-2, the virus that causes COVID-19, from vaccination or infection. This is known as seroprevalence. The nationwide blood donor seroprevalence survey will help in identifying the percentage of the U.S. population that has been infected with the virus or has developed antibodies after being vaccinated against COVID-19.