Estimated seroprevalence of SARS-CoV-2 antibodies among adults in Orange County, California.

Affiliation

Bruckner TA(1), Parker DM(2), Bartell SM(2)(3), Vieira VM(2), Khan S(4), Noymer A(2), Drum E(2), Albala B(5), Zahn M(6), Boden-Albala B(7).
Author information:
(1)Program in Public Health, University of California, Irvine, 653 E. Peltason Dr, Irvine, CA, 92697, USA. [Email]
(2)Program in Public Health, University of California, Irvine, 653 E. Peltason Dr, Irvine, CA, 92697, USA.
(3)Department of Statistics, University of California, Irvine, Bren Hall 2019, Irvine, CA, 92697-1250, USA.
(4)School of Medicine, University of California, Irvine, 1001 Health Sciences Rd, Irvine, CA, 92697, USA.
(5)Center for Clinical Research, School of Medicine, University of California, Irvine, 1001 Health Sciences Rd, Irvine, CA, 92617, USA.
(6)Orange County Health Care Agency, 405 W. 5th St., Santa Ana, CA, 92701, USA.
(7)Program in Public Health, University of California, Irvine, 653 E. Peltason Dr, Irvine, CA, 92697, USA. [Email]

Abstract

Clinic-based estimates of SARS-CoV-2 may considerably underestimate the total number of infections. Access to testing in the US has been heterogeneous and symptoms vary widely in infected persons. Public health surveillance efforts and metrics are therefore hampered by underreporting. We set out to provide a minimally biased estimate of SARS-CoV-2 seroprevalence among adults for a large and diverse county (Orange County, CA, population 3.2 million). We implemented a surveillance study that minimizes response bias by recruiting adults to answer a survey without knowledge of later being offered SARS-CoV-2 test. Several methodologies were used to retrieve a population-representative sample. Participants (n = 2979) visited one of 11 drive-thru test sites from July 10th to August 16th, 2020 (or received an in-home visit) to provide a finger pin-prick sample. We applied a robust SARS-CoV-2 Antigen Microarray technology, which has superior measurement validity relative to FDA-approved tests. Participants include a broad age, gender, racial/ethnic, and income representation. Adjusted seroprevalence of SARS-CoV-2 infection was 11.5% (95% CI: 10.5-12.4%). Formal bias analyses produced similar results. Prevalence was elevated among Hispanics (vs. other non-Hispanic: prevalence ratio [PR] = 1.47, 95% CI 1.22-1.78) and household income < $50,000 (vs. > $100,000: PR = 1.42, 95% CI: 1.14 to 1.79). Results from a diverse population using a highly specific and sensitive microarray indicate a SARS-CoV-2 seroprevalence of ~ 12 percent. This population-based seroprevalence is seven-fold greater than that using official County statistics. In this region, SARS-CoV-2 also disproportionately affects Hispanic and low-income adults.