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Half of U.S. Adults Have Hybrid COVID-19 Immunity

June 27, 2023

What is the prevalence of SARS-CoV-2 antibodies among U.S. adults? New data indicate both infection-induced and hybrid immunity increased from spring 2021 to fall 2022. These findings appear in a recent article, “Estimates of SARS-CoV-2 Seroprevalence and Incidence of Primary SARS-CoV-2 Infections Among Blood Donors, by COVID-19 Vaccination Status — United States, April 2021–September 2022”, published in Morbidity and Mortality Weekly Report (MMWR). Authors, including Westat researchers Jean Opsomer, PhD, and Irene Molina Manrique, MS, describe the prevalence of infection-induced, vaccination-induced, and hybrid immunity (antibodies from both infection and vaccination) to COVID-19. The data are from a nationwide cohort of blood donors who donated blood at least 2 times in the preceding year.

The study is funded by the Centers for Disease Control and Prevention (CDC) with Westat partnering with Vitalant Research Institute, the American Red Cross, and Creative Testing Solutions. Blood donations from cohort members are tested for SARS-CoV-2 antibodies, and Westat researchers provide data management, analysis, and coordination. See the CDC’s COVID Data Tracker.

The research indicates that by the 3rd quarter of 2022,

  • Approximately 96% of persons aged ≥16 years had SARS-CoV-2 antibodies from previous infection or vaccination.
  • 70.3% of persons had been infected, and 47.7% of persons had hybrid immunity.
  • Hybrid immunity was highest among those aged 16 to 29 years and lowest among persons aged ≥65 years, likely due to higher vaccination coverage and earlier availability of COVID-19 vaccines for the older age group.
  • The incidence of first-time SARS-CoV-2 infection was lower among persons who had received COVID-19 vaccine than among unvaccinated persons.

Results from this study provide important insights into the SARS-CoV-2 seroprevalence and incidence of primary infections among blood donors in the U.S. In addition, study findings are reflective of the success of public health interventions and emphasize the continued need for COVID-19 vaccination.


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