Prevalence of SARS-CoV-2 Antibodies in a Multistate Academic Medical Center

Abstract

Objective To estimate the seroprevalence of SARS-CoV-2 antibodies in healthcare personnel. Methods The Mayo Clinic Serology Screening Program was created to provide a voluntary, two-stage testing program for SARS-CoV-2 antibodies to healthcare personnel. The first stage utilized a dried blood spot screening test initiated on June 15, 2020. Those participants identified as reactive were advised to have confirmatory testing via a venipuncture. Venipuncture results through August 8, 2020 were considered. Consent and authorization for testing was required in order to participate in the screening program. This report, which was conducted under an institutional review board approved protocol, only includes employees who have further authorized their records for use in research. Results A total of 81,113 healthcare personnel were eligible for the program, and of these 29,606 participated in the screening program. A total of 4,284 (14.5%) of the dried blood spot test results were “reactive” and warranted confirmatory testing. Confirmatory testing was completed on 4,094 (96%) of the screen reactive with an overall seroprevalence rate of 0.60% (95% CI: 0.52% to 0.69%). Significant variation in seroprevalence was observed by region of the country and age group. Conclusions The seroprevalence for SARS-CoV-2 antibodies through August 8, 2020 was found to be lower than previously reported in other health care organizations. There was an observation that seroprevalence may be associated with community disease burden.

Reported exposure trends among healthcare personnel COVID-19 cases, USA, March 2020–March 2021

“…Workplaces are microcosms of the community in which frequency of infectious contacts broadly parallels community incidence; high community incidence may increase both occupational and nonoccupational exposures. 9 However, the association between community incidence and HCP COVID-19 case exposure setting remains unstudied.…”

SARS-CoV-2 Period Seroprevalence and Related Factors, Hillsborough County, Florida, USA, October 2020–March 2021

“…Infection rates among adults with high exposure to COVID-19 is likely multifactorial and varies from population to population on the basis of contextual factors, which can be demonstrated by seroprevalence studies conducted in large healthcare systems of healthcare workers with high exposure to COVID-19. For example, the seroprevalence of healthcare personnel tested during June–August 2020 throughout all Mayo Clinic facilities was only 0.6%, and areas undergoing greater community disease transmission and burden were associated with higher seroprevalence among healthcare providers ( 20 ). Notably, the Mayo Clinic in Florida had a seroprevalence of 0.8%.…”

Validation of a multiplex flow immunoassay for detection of IgG antibodies against SARS-CoV-2 in dried blood spots

“…Notably however, these studies were primarily done using either in-house developed ELISAs without FDA EUA, or the Euroimmun anti-SARS-CoV-2 IgG ELISA. Prior experience in our laboratory using the Euroimmun ELISA on DBS extracts was associated with limited specificity (~86%) as compared to results in matched serum samples tested by an alternative, high-throughput SARS-CoV-2 serologic assay with FDA EUA [ 1 , 2 ]. We therefore selected to evaluate the Luminex xMAP multi-antigen SARS-CoV-2 serologic assay for use on DBS as it separately measures IgG reactivity against three viral antigens (NC, RBD and S1), which is consistent with national guidelines to assess a multi-target immune response to SARS-CoV-2, especially in low-prevalence settings, in an effort to improve the positive predictive value of serologic assays [ 15 ].…”

“…Paired serum and DBS samples collected from 159 unique individuals with a median age of 44 years (range 21 to 70 years) and of whom 119 (74.8%) were female, were used for this study. Among these 159 paired samples, 139 specimens were selected and de-identified from participants of the Mayo Clinic employee seroprevalence study [ 2 ]. Paired DBS and serum samples were collected a median of 1 day apart (range: 1 to 22 days).…”

“…We previously validated DBS samples as an alternative to serum, for detection of IgG-class antibodies against the SARS-CoV-2 spike glycoprotein using the Euroimmun anti-SARS-CoV-2 IgG ELISA (Euroimmun, Lübeck, Germany), which has FDA EUA for use on serum or plasma [ 1 ]. The modified Euroimmun ELISA performed on DBS extracts was the backbone method used for a large scale HCW SARS-CoV-2 seroprevalence study at Mayo Clinic, where nearly 30,000 volunteer participants were screened over a 6-week period [ 2 ]. Notably however, due to a high level of false positive results generated by the Euroimmun ELISA on DBS (~ 15%), a two-tier testing approach was implemented for the Mayo Clinic employee seroprevalence study: any DBS reactive result by the Euroimmun ELISA on DBS required confirmation using a venipuncture collected serum sample tested by the Roche Diagnostics Elecsys Anti-SARS-CoV-2 Total Antibody electrochemiluminescence immunoassay (ECLIA; Roche Diagnostics, Indianapolis, IN).…”