Coronavirus Disease 2019 infections among healthcare workers were widely reported in China and Europe as the pandemic expanded to the United States. In order to examine the infection rate among these essential workers, we combined results of SARS-CoV-2 serology testing offered free to healthcare workers at two large San Diego health systems when the antibody assays first became available

Case, Jamie

Fitzgerald, Robert L

Kurian, Sunil

Marsh, Christopher

McLawhon, Ronald W

Nicholson, Laura

Quigley, Michael

eScholarship - University of California

UC San DiegoUC San Diego Previously Published WorksTitleHealthcare worker seroconversion for SARS-CoV-2 at two large health systems in San DiegoPermalinkhttps://escholarship.org/uc/item/2tv7k8nfJournalAmerican Journal of Infection Control, 49(4)ISSN0196-6553AuthorsNicholson, LauraMcLawhon, Ronald WKurian, Sunilet al.Publication Date2021-04-01DOI10.1016/j.ajic.2020.12.017 Peer reviewedeScholarship.org Powered by the California Digital LibraryUniversity of California  Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website.  Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.  American Journal of Infection Control 49 (2021) 506−507Contents lists available at ScienceDirectAmerican Journal of Infection Controljournal homepage: www.aj ic journal .orgBrief ReportHealthcare worker seroconversion for SARS-CoV-2 at two large healthsystems in San DiegoLaura Nicholson MD, PhD a,*, Ronald W. McLawhon MD, PhD b, Sunil Kurian PhD c, Robert L. Fitzgerald PhD b,Jamie Case PhD c, Christopher Marsh MD c, Michael Quigley MDda Scripps Clinic, Department of Medicine, La Jolla, CAb University of California San Diego Health, Department of Pathology, La Jolla, CAc Scripps Clinic, Department of Surgery, La Jolla, CAd Scripps Clinic, Department of Pathology, La Jolla, CAKey Words:* Address correspondence to Laura Nicholson, MD,Group, 10666 North Torrey Pines Road, 404C, La Jolla, CAE-mail address: Nicholson.Laura@scrippshealth.org (LConflicts of Interest: The 7 authors listed above drelated to this manuscript.https://doi.org/10.1016/j.ajic.2020.12.0170196-6553/© 2021 The Author(s). Published by Elsevier Ithe CC BY-NC-ND license (http://creativecommons.org/liCoronavirus Disease 2019 infections among healthcare workers were widely reported in China and Europe asthe pandemic expanded to the United States. In order to examine the infection rate among these essentialworkers, we combined results of SARS-CoV-2 serology testing offered free to healthcare workers at two largeSan Diego health systems when the antibody assays first became available.© 2021 The Author(s). Published by Elsevier Inc. on behalf of Association for Professionals in Infection Controland Epidemiology, Inc. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/)SeroprevalenceCOVID-19Frontline providersPhD, Scripps Clinic Medical92037.. Nicholson).eclare no conflict of interestsnc. on behalf of Association for Professionals in Infection Control and Epidemiology, Inc. This is an open access article undercenses/by-nc-nd/4.0/)INTRODUCTIONSan Diego confirmed its first case of Coronavirus Disease 2019(COVID-19) on March 9, 2020, 12 days after the first nontravel-related infection in the United States was diagnosed in California.1Personal protective equipment (PPE) was in limited supply at theonset of the pandemic, and occupational infections of healthcareworkers (HCW) were increasingly reported.2 While polymerasechain reaction (PCR) to detect viral nucleic acid is the mainstay fordiagnosing acute COVID-19 disease, it has been intermittentlyreserved for only the most symptomatic individuals, particularlyearly in the outbreak. Thus PCR-positive case rates underrepresentthe true penetrance of SARS-CoV-2 infection, and seroprevalencesurveys allow for more accurate insight into population exposure.3Additionally, in late winter 2020, multiple respiratory illnesses cir-culated in the population and many with mild symptoms believedthey may have COVID-19 disease but were unable to obtain a test.Two large San Diego health systems offered SARS-CoV-2 serologytests free of charge for employees, in part to better illuminateworkforce infection rates at sites caring for San Diego’s earlyCOVID-19 patients.METHODSTwo multi-hospital San Diego healthcare systems offered freeSARS CoV-2 IgG tests to their employees considered at risk forexposure − University of California San Diego Health (UCSD)invited 11,801 HCW beginning in April, and used Diazyme DZ-Lite2019-nCoV IgG (CLIA) Assay on the DZ-Lite 3000 Plus, reporting94.7% sensitivity and 99.1% specificity; Scripps Health invited12,143 HCW beginning in May, using the Abbott Architect SARS-CoV-2 IgG assay, validating at 100% sensitivity and 99.6% specific-ity. Email invitations and flyers were distributed to workers inCOVID-19 care areas, though confirmation of work area was notrequired at testing. Employees actively experiencing symptomswere asked not to participate in this screening and instead referredfor clinical evaluation. All assays were conducted in certified clini-cal laboratories, and results were provided in accordance withHealth Information Portability and Accountability Act regulations.De-identified results from the two health systems were combinedin a posthoc analysis to provide a broader picture of HCW SARS-CoV-2exposure early in the pandemic in San Diego County.RESULTSUCSD conducted 13,549 tests among 9,939 unique asymptomaticHCW between April 14 and July 28, 2020, and 97 (0.98%) were posi-tive (Table 1). Scripps Health tested 2,054 HCW between May 27 andJune 30, 2020, and 16 (0.78%) were positive. Combined, 113 of 11,993Table 1Total number of SARS-CoV-2 IgG tests and positives in 2-week intervals at UCSD and ScrippsDates Tests UCSD Positives UCSD Tests Scripps Positives ScrippsApr 14-30 1,715 9May 1-15 3,489 26May 16-31 2,760 14 189 1June 1-15 2,036 16 970 5June 16-30 1,734 19 895 10July 1-15 1,124 17July 16-28 691 12Totals (unique HCW)* 13,549 (9,939) 113 (97) 2,054 (2,054) 16 (16)*UCSD offered repeat serology testing among its HCW; Scripps offered only 1 serology test per HCW.L. Nicholson et al. / American Journal of Infection Control 49 (2021) 506−507 507(0.94%) were positive across the two health systems. At UCSD, HCWroles were not specifically queried during testing. At Scripps, roleswere surveyed with an open-ended question, and >400 uniqueresponses were counted as 228 physicians, 734 nurses, and 1092ancillary staff. Scripps’ positives included 7 nurses, 2 hospital environ-mental services personnel, 1 surgeon, 1 physical therapist, 1 ultrasoundtechnician, 1 patient care assistant, 1 food service worker, 1 transporter,and 1 information services technician.DISCUSSIONSan Diego County, the fifth most populated county in the UnitedStates, reported 29,577 PCR-confirmed COVID-19 cases as of July 31,among its 3.3 million populace.4 Conservatively assuming 6 unre-corded infections for each PCR-confirmed case produces an estimatedcommunity prevalence of 1.1% in late April rising to 5.4% by the endof July.3,4 Our HCW 0.94% seroprevalence collected across this timeperiod indicates an occupational exposure very likely lower than thecommunity infection rate, particularly given that a percentage, esti-mated at 5%-45% based on test characteristics, are expected to befalsely positive during the low April-July prevalence.CONCLUSIONSReports from China, Europe, and New York led to the assumptionthat HCW SARS-CoV-2 occupational infection would be common andunavoidable in settings where care of COVID-19 patients takes place.5-7Our results demonstrate that occupational COVID-19 infection risk ismuch lower in our setting than originally feared, even with clinical carelimited to urgent and emergent illness before July. This leads to severalconclusions. First, careful preparation of healthcare environments andworkers allowed safe care of acutely ill COVID-19 patients. San Diegobenefits from an engaged network of researchers and clinicians commu-nicating to leaders regarding preparation for SARS-CoV-2-infectedpatients, leading to active training with PPE and prompt backup work-force planning before the first San Diego COVID-19 patient. Second,locking down March 19, early in the outbreak with fewer than 100known San Diego cases, was effective in protecting frontline workers bypreventing an overwhelmed healthcare environment, in contrast toareas with less forewarning and subsequent higher HCW seroconver-sion.8 Third, PPE works. Our HCW, consistently using PPE in the work-place, appear to have had a lower infection risk than the community assimilarly reported elsewhere, providing strong evidence for the value offace masks and adherence to infection control measures in the generalpopulation.6,8 Finally, respiratory illnesses circulating in HCW at thestart of San Diego’s outbreak were predominantly not COVID-19, sup-ported by the low HCW seropositivity rate in the first 150 days of SanDiego’s outbreak combined with the excellent specificity of these IgGassays, and consistent with reported retrospective sample testing.1In summary, our analysis illustrates a low infection rate and con-tinued vulnerability among San Diego’s healthcare workforce to theCOVID-19 pandemic and affirms the need for adequate PPE, clinicalstaffing support, careful contact tracing, behavioral education, andvaccination when available. Limitations include different SARS-CoV-2IgG assays and testing periods between the 2 centers, due to repeatedpostponement of available tests and their validation requirements,and the possibility that some HCW with early infections had becomeseronegative before assays were available. Additionally, our sero-prevalence result may be an underestimate if previously confirmed(SARS-CoV-2 PCR+) HCW were less likely to seek antibody confirma-tion, or an overestimate if more HCW from higher risk work environ-ments presented for participation. While COVID-19 patient contactor care location was not required to qualify for testing, many partici-pants were working regularly in healthcare environments providingurgent, acute care while routine care was suspended. Lower sero-prevalence in settings thus enriched for the presence of SARS-CoV-2,compared to community prevalence, provides important infectioncontrol information.AcknowledgmentsWe would like to acknowledge the assistance of Rowena Carino,MA, Michelle Meyer, MSN, and Bethany Barrick, BS, in collecting,resulting, and compiling the serology assays.References1. CDC COVID-19 Response Team. Jorden MA, Rudman SL, Villarino E, et al. Evidencefor limited early spread of COVID-19 within the United States, January-February2020.MMWRMorb Mortal Wkly Rep. 2020;69:680−684.2. One in 7 Reported COVID-19 Infections is Among Health Workers, WHO Says. Reuters.com; 2020. September 17. Available at: https://www.reuters.com/article/us-health-coronavirus-who-healthworkers/one-in-7-reported-covid-19-infections-is-among-health-workers-who-says-idUSKBN2681TR?il=0. Accessed September 25, 2020.3. Havers FP, Reed C, Lim T, et al. Seroprevalence of antibodies to SARS-CoV-2 in 10sites in the United States, March 23-May 12, 2020. JAMA Intern Med. 2020;180:1576−1586.4. County of San Diego Coronavirus Disease (COVID-19) Dashboard. Available at:https://www.arcgis.com/apps/opsdashboard/index.html#/96feda77f12f46638b984fcb1d17bd24. Accessed September 25, 2020.5. Mansour M, Leven E, Muellers K, Stone K, Mendu DR, Wajnberg A. Prevalence ofSARS-CoV-2 antibodies among healthcare workers at a tertiary academic hospitalin New York City. J Gen Intern Med. 2020;35:2485–2486.6. Steensels D, Oris E, Coninx L, et al. Hospital-wide SARS-CoV-2 antibody screening in3056 staff in a tertiary center in Belgium. JAMA. 2020;324:195–197.7. Xu X, Sun J, Nie S, et al. Seroprevalence of immunoglobulin M and G antibodiesagainst SARS-CoV-2 in China. Nat Med. 2020;26:1193–1195.8. NY Frontline Workers Test Positive for Antibodies at Lower Rates than Rest of State.NBCNewYork.com; 2020. Available at: https://www.nbcnewyork.com/news/coro-navirus/cuomo-ny-frontline-workers-test-positive-for-covid-antibodies-at-lower-rate-than-rest-of-state/2415595/. Accessed September 25, 2020.

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Healthcare worker seroconversion for SARS-CoV-2 at two large health systems in San Diego

Healthcare worker seroconversion for SARS-CoV-2 at two large health systems in San Diego

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