2020-2021 Nationwide Blood Donor Seroprevalence Survey Combined Infection- and Vaccination-Induced Seroprevalence Estimates

This is the largest nationwide COVID-19 seroprevalence survey to date. De-identified blood samples are tested for antibodies to SARS-CoV-2 to better understand the percentage of people in the United States who have antibodies against SARS-CoV-2 (the virus that causes COVID-19) and to track how this percentage changes over time.

Both SARS-CoV-2 infection and COVID-19 vaccines currently used in the United States result in production of anti-spike (anti-S) antibodies but only infection results in production of anti-nucleocapsid (anti-N) antibodies. Combined seroprevalence estimates the proportion of the population with evidence of previous SARS-CoV-2 infection, COVID-19 vaccination, or both. It estimates the proportion of the population with some presumed protection against infection with the virus that causes COVID-19.