Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Aug 22;17(8):e0272783.
doi: 10.1371/journal.pone.0272783. eCollection 2022.

Anti-SARS-CoV-2 seroprevalence in King County, WA-Cross-sectional survey, August 2020

Karen D Cowgill  1 , Elena A Erosheva  2 , Adam Elder  3 , Ljubomir Miljacic  4 , Susan Buskin  5   6 , Jeffrey S Duchin  5   6   7
Affiliations

Anti-SARS-CoV-2 seroprevalence in King County, WA-Cross-sectional survey, August 2020

Karen D Cowgill et al. PLoS One. .

Abstract

We conducted a seroprevalence survey to estimate the true number of infections with SARS-CoV-2, the virus that causes COVID-19, in King County as of August 2020 by measuring the proportion of residents from who had antibodies against the virus. Participants from 727 households took part in a cross-sectional address-based household survey with random and non-random samples and provided dried blood spots that were tested for total antibody against the viral nucleocapsid protein, with confirmatory testing for immunoglobulin G against the spike protein. The data were weighted to match King County's population based on sex, age group, income, race, and Hispanic status. After weighting and accounting for the accuracy of the tests, our best overall estimate of anti-SARS-CoV-2 seroprevalence in King County as of August 2020 is 3.9% (95% confidence interval (CI) 2.4%-6.0%) with an effective sample size of 589. Comparing seroprevalence with positive test reports, our survey suggests that viral testing underestimated incidence by a factor of about five and suggests that the proportion of cases that were serious (based on hospitalization) or fatal was 2.4% and 0.8%, respectively. Prevalence varied by subgroup; households reporting incomes at or below $100,000 in 2019 had nearly five times higher estimated antibody prevalence than those with incomes above $100,000. Those reporting non-White/non-Asian race had roughly seven times higher estimated antibody prevalence than those reporting White race. This survey was noteworthy for including people of all ages; among all age groups, the weighted estimate of prevalence was highest in older teens and young adults and lowest in young children, although these differences were not statistically significant.

PubMed Disclaimer

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Database architecture, King County, WA COVID-19 antibody testing survey, August 2020.
Fig 2
Fig 2. Estimated anti-SARS-CoV-2 seroprevalence across race group in King County in early-to-mid-August 2020.
Points indicate estimates and lines indicate 95% confidence intervals.
Fig 3
Fig 3
Estimated anti-SARS-CoV-2 seroprevalence across sex in King County in early-to-mid-August 2020. Points indicate estimates and lines indicate 95% confidence intervals.
Fig 4
Fig 4. Estimated anti-SARS-CoV-2 seroprevalence across income categories in King County in early-to-mid-August 2020.
Income categories in United States dollars. Points indicate estimates and lines indicate 95% confidence intervals.
Fig 5
Fig 5. Estimated anti-SARS-CoV-2 seroprevalence across age group in King County in early-to-mid-August 2020.
Age in years. Points indicate estimates and lines indicate 95% confidence intervals.
See this image and copyright information in PMC

References

    1. Jorden MA, Rudman SL, Villarina E, et al.. Evidence for Limited Early Spread of COVID-19 Within the United States, January–February 2020. MMWR Morb Mortal Wkly Rep. 2020;69: 680–84. doi: 10.15585/mmwr.mm6922e1 - DOI - PMC - PubMed
    1. Public Health—Seattle & King County COVID-19 Outbreak Summary: Testing volume and percent positive by Geography over Time [Internet]. [cited 19 Mar 2021]. Available: https://www.kingcounty.gov/depts/health/covid-19/data/daily-summary.aspx
    1. Angulo FJ, Finelli L, Swerdlow DL. Estimation of US SARS-CoV-2 Infections, Symptomatic Infections, Hospitalizations, and Deaths Using Seroprevalence Surveys. JAMA Netw open. 2021;4: e2033706. doi: 10.1001/jamanetworkopen.2020.33706 - DOI - PMC - PubMed
    1. Wu SL, Mertens AN, Crider YS, Nguyen A, Pokpongkiat NN, Djajadi S, et al.. Substantial underestimation of SARS-CoV-2 infection in the United States. Nat Commun. Springer; US; 2020;11. doi: 10.1038/s41467-020-18272-4 - DOI - PMC - PubMed
    1. Washington State Office of Financial Management. Estimates of April 1 population by age, sex, race and Hispanic origin [Internet]. 2021 [cited 19 Mar 2021]. Available: https://ofm.wa.gov/washington-data-research/population-demographics/popu...

Publication types

Substances