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In December 2021, the B. 1.1. 529 (Omicron) variant of SARS-CoV-2, the virus that causes COVID-19, became predominant in the United States. Subsequently, national COVID-19 case rates peaked at their highest recorded levels.* Traditional methods of disease surveillance do not capture all COVID-19 cases because some are asymptomatic, not diagnosed, or not reported; therefore, the proportion of the population with SARS-CoV-2 antibodies (ie, seroprevalence) can improve understanding of population-level incidence of COVID-19. This report uses data from CDC’s national commercial laboratory seroprevalence study and the 2018 American Community Survey to examine US trends in infection-induced SARS-CoV-2 seroprevalence during September 2021–February 2022, by age group.

The national commercial laboratory seroprevalence study is a repeated, cross-sectional, national survey that estimates the proportion of the population in 50 US states, the District of Columbia, and Puerto Rico that has infection-induced antibodies to SARS-CoV-2.† Sera are tested for anti-nucleocapsid (anti-N) antibodies, which are produced in response to infection but are not produced in response to COVID-19 vaccines currently authorized for emergency use or approved by the Food and Drug Administration in the United States. §