Prevalence and Longevity of SARS-CoV-2 Antibodies in Healthcare Workers: A Single Center Study

Brant-Zawadzki, M.; Fridman, D.; Robinson, P.; Zahn, M.; Chau, C.; German, R.; Breit, M.; Burke, E.; Bock, J. R.; Hara, J.

Understanding SARS-CoV-2 antibody prevalence as a marker of prior infection in a spectrum of healthcare workers (HCWs) may guide risk stratification and enactment of better health policies and procedures. The present study reported on cross-sectional study to determine the prevalence and longevity of SARS-CoV-2 antibodies in HCWs at a regional hospital system in Orange County, California, between May and August, 2020. Data from HCWs (n=3,458) were included in the analysis. Data from first responders (n=226) were also analyzed for comparison. A blood sample was collected at study enrollment and 8-week follow-up. Information on job duties, location, COVID-19 symptoms, polymerase chain reaction test history, travel since January 2020, and household contacts with COVID-19 was collected. Comparisons to estimated community prevalence were also evaluated. Observed antibody prevalence was 0.93% and 2.58% at initial and 8-week follow-up, respectively, for HCWs, and 5.31% and 4.35% for first responders. For HCWs, significant differences (p < .05) between negative vs. positive at initial assessment were found for age, race, fever, and loss of smell, and at 8-week follow-up for age, race, and all symptoms. Antibody positivity persisted at least 8 weeks in this cohort. Among 75 HCWs with self-reported prior PCR-confirmed COVID-19, 35 (46.7%) were antibody negative. Significant differences between negative vs. positive were observed in age and frequency of symptoms. This study found considerably lower SARS-CoV-2 antibody prevalence among HCWs compared with prior published studies. This may be explained by better safety measures in the workplace, heightened awareness inside and outside of the workplace, possibly lower susceptibility due to innate immunity and other biological heterogeneity, and low COVID-19 prevalence in the community itself. HCWs with initial positive results had persistent positive serologies at 8 weeks. Further research is warranted to investigate factors influencing such lower prevalence in our HCWs.