key: cord-0792258-z4mqkc0t authors: Galanis, P. A.; Vraka, I.; Fragkou, D.; Bilali, A.; Kaitelidou, D. title: Seroprevalence of SARS-CoV-2 antibodies and associated factors in health care workers: a systematic review and meta-analysis date: 2020-10-27 journal: nan DOI: 10.1101/2020.10.23.20218289 sha: d964502a37fd618e95e3d84f2ff5cc43dac8260d doc_id: 792258 cord_uid: z4mqkc0t Background: Health care workers (HCWs) represent a high risk population for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Aim: To determine the seroprevalence of SARS-CoV-2 antibodies among HCWs, and to find out the factors that are associated with this seroprevalence. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were applied for this systematic review and meta-analysis. Databases including PubMed/MEDLINE and pre-print services (medR{chi}iv and bioR{chi}iv) were searched from inception up to August 24, 2020. Findings: Fifty studies, including 184,898 HCWs met the inclusion criteria. The estimated overall seroprevalence of SARS-CoV-2 antibodies among HCWs was 8.4% (95% CI: 6.1-11.1%). Seroprevalence was higher in studies that were conducted in North America (12.7%) compared to those in Africa (8.2), Europe (8.1%) and Asia (4%). Meta-regression showed that increased sensitivity of antibodies test was associated with increased seroprevalence. The following factors were associated with seropositivity: male gender, Black, Asian, and Hispanic HCWs, work in a coronavirus disease 2019 (COVID-19) unit, patient-related work, frontline health care workers, health care assistants, personal protective equipment shortage, self-reported belief for previous SARS-CoV-2 infection, previous positive polymerase chain reaction test, and household contact with suspected or confirmed COVID-19 patients. Conclusion: The seroprevalence of SARS-CoV-2 antibodies among HCWs is high. Excellent adherence to infection prevention and control measures, sufficient and adequate personal protective equipment, and early recognition, identification and isolation of HCWs that are infected with SARS-CoV-2 are imperative to decrease the risk of SARS-CoV-2 infection. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease 2019 (COVID-19) emerged from the Wuhan, Hubei province, China during December 2019 and the World Health Organization (WHO) declared a world pandemic on 11 th March 2020 [1] . As of October 2, 2020, the WHO reported 34,079,542 cases globally and 1,015,963 deaths due to COVID-19 [2] . Health care workers (HCWs) are a high risk group for infection and a recent metaanalysis with 11 studies found that the proportion of HCWs who were SARS-CoV-2 positive among all COVID-19 patients was 10.1% but the severity and mortality among HCWs were lower than COVID-19 patients [3] . This proportion varied substantially among countries i.e. China; 4.2%, Italy; 9% and USA; 17.8% [3] . Lower proportion in China is probably due to implementation of immediate and strong public health interventions e.g. lockdown measures, home isolation, quarantine measures, wearing masks and social (physical) distancing [4] . SARS-CoV-2 and COVID-19 present significant diagnostic issues i.e. serology tests aim to identify previous SARS-CoV-2 infection detecting the presence of SARS-CoV-2 antibodies. Until now, it is known that SARS-CoV-2 antibodies tests are accurate to detect previous SARS-CoV-2 infection if used >14 days after the onset of symptoms and they have very low sensitivity in the first week since symptoms onset [5] . Also, rapid diagnostic tests for SARS-CoV-2 antibodies show a low pooled sensitivity (64.8) and a high pooled specificity (98%) but this meta-analysis suffers from low power and other significant limitations [6] . Knowing seroprevalence of SARS-CoV-2 antibodies among HCWs is important to understand COVID-19 spread among health care facilities and to assess the success of public health interventions. To our knowledge, the overall seroprevalence of SARS-CoV-2 antibodies among HCWs and the associated factors are unknown. Thus, the primary objective of this systematic review and meta-analysis was to determine the seroprevalence of SARS-CoV-2 antibodies among HCWs, while the secondary objective was to find out the factors that are associated with this seroprevalence. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; https://doi.org/10.1101/2020.10.23.20218289 doi: medRxiv preprint 4 The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were applied for this systematic review and meta-analysis [7] . PRISMA checklist is presented in Web Table 1 . We searched PubMed/MEDLINE and pre-print services (medRχiv and bioRχiv) from inception up to August 24, 2020 . Also, we examined reference lists of all relevant articles and we removed duplicates. We used the following search strategy: ("sars-cov-2 antibodies" OR "COVID-19 antibodies" OR "sars-cov-2" OR "COVID-19" OR antibodies) AND ("health care personnel" OR "healthcare personnel" OR "health-care personnel" OR "health care workers" OR "health-care workers" OR "healthcare workers" OR "healthcare staff" OR "health care staff" OR "health-care staff" OR "medical staff"). Two independent review authors performed study selection and a third, senior author resolved the discrepancies. We included all studies that were written in English, except case reports. Also, we included studies that reported the seroprevalence of SARS-CoV-2 antibodies among HCWs and the associated factors. We searched for any serology test (e.g. ELISA, CLIA, etc.) detects SARS-CoV-2 antibodies (IgA, IgG, and IgM) in all HCWs. Moreover, we included studies that were performed under screening settings and HCWs were neither selected for participation based on previous exposure to SARS-CoV-2 nor symptoms. Data collected included study characteristics such as authors, location, data collection time, sample size, setting, study design, antibodies test, sensitivity and specificity for the antibodies test, number of HCWs with SARS-CoV-2 antibodies, factors associated . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; https://doi.org/10.1101/2020.10.23.20218289 doi: medRxiv preprint with the seroprevalence of SARS-CoV-2 antibodies, and the level of analysis (univariate or multivariable). The quality of the studies was assessed with the Joanna Briggs Institute critical appraisal tools where a 9-point scale is used for prevalence studies, an 8-point scale for cross-sectional studies and an 11-point scale for cohort studies [8] . In prevalence studies, a score of 8-9 points indicates good quality, a score of 5-7 points indicates moderate quality and a score ≤ 4 indicates poor quality. In cross-sectional studies, a score of 7-8 points indicates good quality, a score of 4-6 points indicates moderate quality and a score ≤ 3 indicates poor quality. In cohort studies, a score of 9-11 points indicates good quality, a score of 5-8 points indicates moderate quality and a score ≤ 4 indicates poor quality. For each study we extracted the total number of HCWs and the number of HCWs that were positive for SARS-CoV-2 antibodies. The seroprevalence and the 95% confidence interval (CI) were calculated for each included study. We transformed seroprevalences with the Freeman-Tukey Double Arcsine method before pooling [9]. Between-studies heterogeneity was assessed by the Hedges Q statistic and I 2 statistics. Statistical significance for the Hedges Q statistic is set at p-value < 0.1, while I 2 values higher than 75% indicates high heterogeneity [10]. We applied a random effect model to estimate pooled seroprevalence since the heterogeneity between results was very high [10-11]. We considered studies quality, sample size, sensitivity and specificity for the antibodies tests, publication type (journal or pre-print service) and the continent that studies were conducted as pre-specified sources of heterogeneity and we explored them with subgroup analysis and meta-regression analysis. Also, we performed a leave-one-out sensitivity analysis by removing one study at a time to determine the influence of each study on the overall prevalence. We used a funnel plot and the Egger's test to assess the publication bias. P-value < 0.05 for the Egger's test indicates publication bias [12]. We did not perform meta-analysis for the factors that are associated with the seroprevalence of SARS-CoV-2 antibodies since the data were very scarce. Statistical analysis was performed with OpenMeta[Analyst] [13]. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted October 27, 2020. ; https://doi.org/10.1101/2020.10.23.20218289 doi: medRxiv preprint Flowchart of the literature search is summarized in PRISMA format ( Figure 1 ). Initially, we identified 3632 potential records through PubMed and 103 records through preprint servers for health sciences i.e. medRχiv and bioRχiv removing duplicates. After the screening of the titles and abstracts, we removed 3684 records and we added 12 more records found by the reference lists scanning. Finally, we included 49 studies in this meta-analysis that met our inclusion criteria. Main characteristics of the 49 studies included in our systematic review and metaanalysis are shown in Table 1 . A total of 127,480 HCWs were included in this systematic review and meta-analysis. Forty-nine studies reported data regarding the seroprevalence of SARS-CoV-2 antibodies among HCWs and 27 studies [14, 15, 18, 19, 21-25, 27-32, 34-37, 39, 44, 47, 52, 54, 58, 60, 61] investigated factors for SARS-CoV-2 antibodies positivity. The majority of studies was conducted in Europe (n=31), and then in North America (n=9), Asia (n=6), and Africa (n=3). In particular, nine studies was conducted in USA [14, 15, 24, 26, 27, 29, 32, 34, 40] [17, 18, 21, 23, 32, 33, 36, 41, 48] , eight studies did not report sex distribution [16, 18, 21, 25, 32, 33, 41, 48] and five studies did not report data collection time [17, 36, 43 Validity assessment (sensitivity and specificity) for the antibodies tests used in the included studies according to the manufacturers data are presented in Web Table 2 . Sensitivity ranged from 50% to 100%, while specificity from 80.5% to 100%. Quality assessment of prevalence studies, cross-sectional studies and cohort studies are shown in Web Tables 3, 4, and 5 respectively. Quality was moderate in 37 studies, good in 10 studies, and poor in two studies. Regarding prevalence studies, 16 were at moderate risk of bias, three were at low risk and one was at high risk. Moreover, 20 cross-sectional studies were at moderate risk of bias, five were at low risk and one was at high risk. Two cohort studies were at low risk of bias and one was at moderate risk. We applied a random effect model to estimate pooled prevalence since the heterogeneity between results was very high (I 2 =99.34, p-value for the Hedges Q statistic < 0.001). The estimated overall seroprevalence of SARS-CoV-2 antibodies among HCWs was 8.7% (95% CI: 6.7-10.9%) ( Figure 2 ). Seroprevalence among studies ranged from 0% to 45.3%. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted October 27, 2020. ; https://doi.org/10.1101/2020.10.23.20218289 doi: medRxiv preprint According to subgroup analysis, seroprevalence of SARS-CoV-2 antibodies was higher for the studies with poor quality (11.6% [95% CI: 0.7-32.7%]) compared to those with moderate quality (8.8% [95% CI: 6.0-12%]) and good quality ( A leave-one-out sensitivity analysis showed that no single study had a disproportional effect on the overall seroprevalence, which varied between 8.2% (95% CI: 6.2-10.3%), with Hoolihan et al. [16] excluded, and 9.0% (95% CI: 6.9-11.2%), with Nakamura et al. [53] excluded (Web Figure 1 ). Egger's test (p=0.0001) and the asymmetrical shape of the funnel plot (Web Figure 2) implied potential publication bias. Twenty-seven studies [14, 15, 18, 19, 21- . Moreover, Self et al. [24] found that HCWs in surgery department (OR=6.47, 95% CI=2.37-17.63) and pediatric intensive care unit (OR=3.77, 95% CI=1.44-9.89, p=0.007) had a significantly higher percentage of SARS-CoV-2 antibodies. Two studies [28, 60] found that SARS-CoV-2 antibodies positivity was higher among health care assistants (OR=1.39, 95% CI=1.05-1.84 and OR=3.8, 95% CI=2.3-6.1). Self et al. [24] found that no use of a face covering for all clinical encounters (p=0.012) and personal protective equipment shortage (p=0.009) increase the probability of a positive SARS-CoV-2 antibodies test in HCWs. Three studies [14, 24, 34] found that HCWs self-reported belief that (s)he previously had COVID-19 (ORs range from 1.23 to 5.67) is associated with SARS-CoV-2 antibodies positivity. Similar results found for HCWs with a previous positive Polymerase Chain Reaction (PCR) test (OR=1.52, 95% CI=1.44-1.60 in one study [14] and p<0.001 in another study [34] ). Also, two studies [18, 36] found that household contact with suspected or confirmed COVID-19 patients increases the probability of a positive SARS-CoV-2 antibodies test in HCWs (OR=3.15, 95% CI=2.33-4.25 in one study [18] and p=0.008 in another study [36] ). . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) 1 0 To our knowledge, this is the first systematic review and meta-analysis that estimates the overall seroprevalence of SARS-CoV-2 antibodies among HCWs in screening settings. We found that the overall seroprevalence was 8.7% with a wide range among studies from 0% to 45.3%. Population-based and community-based studies in USA showed a great variability in seroprevalence of SARS-CoV-2 antibodies from 1.1% to 14.4% [63-67] . Similar studies in Europe [68] [69] [70] and China [71] found very different seroprevalence in general population ranging from 0.23% to 10.9%. These differences in seroprevalence among studies may be attributable to several reasons, e.g. different study populations, different antibodies tests with variation in sensitivity and specificity, different study designs, different lockdown and quarantine measures, different data collection time period etc. Moreover, according to our subgroup analysis, seroprevalence of SARS-CoV-2 antibodies was higher for the studies with poor quality (11.6%) compared to those with moderate quality (8.8%) and good quality (7.9%) indicating that difference in studies quality could be also a significant reason for difference in seroprevalence. Our subgroup analysis identified that seroprevalence was higher in studies that were conducted in North America (12.7%) compared to those in Europe (8.5%), Africa (8.2%), and Asia (4%). This finding is in accordance with a meta-analysis [3] that found that the overall proportion of HCWs who are SARS-CoV-2 positive among all COVID-19 patients is lower in China (4.2%) than in USA (17.8%) and Europe (9%). This might be explained due to the good adherence to infection prevention and control measures and the appropriate use of personal protective equipment among HCWs in China. Also, USA and Europe seem to be unprepared to handle the surge of patients that led to the severe shortage in the personal protective equipment, while USA and most of the countries in Europe (with significant exceptions such as Germany and Greece) took action too late [72] . For example, according to reports in United Kingdom and Italy, HCWs experienced extreme situations during COVID-19 pandemic wearing paper face masks and plastic aprons instead of appropriate masks, visors, and gowns [73, 74] . In our meta-analysis, seroprevalence in studies in United Kingdom (n=7) and Italy (n=8) was higher (10.3%) than the overall seroprevalence (8.4%), while seroprevalence in studies in Germany (n=5) and Greece (n=2) was quite . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) found that seropositivity of HCWs is much higher than this of general population of and would be more prone to viral transmission [73, [80] [81] [82] [83] [84] . Increased HCWs exposure to SARS-CoV-2 may be attributable mainly to patient-to-HCW transmission and HCW-to-HCW transmission due to the personal protective equipment shortage, poor adherence to infection prevention and control measures, and space constraints in hospitals. Additionally, we found that SARS-CoV-2 antibodies positivity was higher among health care assistants [28, 60] a finding that further reinforces a patient-related transmission of SARS-CoV-2 to HCWs since this occupation involves the most patient near contact. In our systematic review, the seroprevalence was higher among HCWs working in a COVID-19 unit [25, 39, 60]. It is clear that HCWs with COVID-19 patient contact have represented a high-risk group for SARS-CoV-2 infection especially during the first months of COVID-19 pandemic where the knowledge, the control measures and the personal protective equipment were limited. Also, Self et al. [24] found that no use of a face covering for all clinical encounters and personal protective equipment shortage increase the probability of a positive SARS-CoV-2 antibodies test in HCWs. Thus, personal protective equipment supplies for HCWs at hospitals are a necessary . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. patients who require admission on an intensive care unit are often admitted around day 10 of the natural history of their illness [90] , by which point viral loads of patients tend to decrease [91] . According to our review, household contact with suspected or confirmed COVID-19 patients is associated with positive SARS-CoV-2 antibodies test in HCWs [18, 36] . Also, HCWs self-reported belief that (s)he previously had COVID-19 is associated with SARS-CoV-2 antibodies positivity [14, 24, 34] . HCWs are exposed to SARS-CoV-2 not only in clinical settings but also in their house or in social meetings, joint meals, and office spaces with friends or colleagues. In fact, as community transmission increases, the risk of SARS-CoV-2 exposure for HCWs is higher outside of the clinical settings through household contacts with infected COVID-19 patients or interaction with others in areas with active, unmitigated transmission [92] [93] [94] . We found that a previous positive PCR test increases the probability of a positive SARS-CoV-2 antibodies test in HCWs [14, 34] . SARS-CoV-2 antibodies tests identify previous SARS-CoV-2 infection but many issues are still controversial. For example, the sensitivity of these tests is too low in the first week since symptom onset but increases ≥ 15 days after the onset of symptoms [5] . Also, the duration of antibody rises is unknown since the data >35 days after the onset of symptoms are very scarce [5] . Moreover, it is currently unknown whether antibody titers correlate with protective immunity against reinfection and if antibody responses differ significantly in asymptomatic individuals and individuals with mild or severe COVID-19 [95, 96] . Variation in the validity of commercial SARS-CoV-2 antibodies tests, cross-reactivity between SARS-CoV-2 and other coronaviruses, and confusion regarding the possible role of SARS-CoV-2 antibodies as biomarkers of protective immunity or past . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) 1 3 infection increase the uncertainty about the utility of SARS-CoV-2 antibodies tests in clinical practice [5, 97, 98] . In any case, SARS-CoV-2 antibodies tests seem to be an additional tool against COVID-19 and their utility will be expanded as additional data give us a better understanding of the pros and cons of these tests. Also, universal screening for SARS-CoV-2 in high-risk units in hospitals could help to identify asymptomatic HCWs resulting on self-isolation for the appropriate time [22] . We identified that seropositivity was higher among African American HCWs [32] and Black, Asian, and Hispanic HCWs compared to White participants [24] . This finding is confirmed by studies in general populations where a higher percentage of SARS-CoV-2 antibodies found among Blacks [67, 99] and Hispanics [67] . According to a preliminary analysis of Cook et al. [ There is a need for strategies tailored to the culture of minority groups and organized by local minority leaders, who can mobilize individuals to participate in screening tests, and tracing and quarantining of COVID-19 contacts to avoid additional SARS- Our study has several limitations. First, 14 out of 49 included studies were published in pre-print services which do not apply peer-review process. Nevertheless, we assessed studies quality and we performed subgroup analysis according to publication type (journal or pre-print service) and studies quality. Second, the heterogeneity between results was very high. We performed random effects model and subgroups analysis to overcome this limitation. Third, seroprevalence reported in studies could be underestimated or overestimated depending on the applied antibody test. Validity is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; 1 4 of the seroprevalence. Last, the data regarding the factors that are associated with the seroprevalence of SARS-CoV-2 antibodies were very scarce and we cannot perform meta-analysis; thus a qualitative approach was applied to assess these factors. Sseroprevalence of SARS-CoV-2 antibodies among HCWs is high indicating that . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; Table 2 . Validity assessment (sensitivity and specificity) for the antibodies tests used in the included studies according to the manufacturers data. Table 3 . Quality of prevalence studies. Web Table 5 . Quality of cohort studies. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. ; https://doi.org/10.1101/2020.10.23.20218289 doi: medRxiv preprint . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. Table 2 . Studies that investigated factors associated with SARS-CoV-2 antibodies positivity among health care workers. Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia World Health Organization. WHO Coronavirus Disease (COVID-19) COVID-19 in health care workers-A systematic review and meta-analysis The impact of novel coronavirus SARS-CoV-2 among healthcare workers in hospitals: An aerial overview 19 Diagnostic Test Accuracy Group. Antibody tests for identification of current and past infection with SARS-CoV-2 Pointof-care diagnostic tests for detecting SARS-CoV-2 antibodies: A systematic review and meta-analysis of real-world data Meta-Analyst: software for meta-analysis of binary, continuous and diagnostic data Northwell Health COVID-19 Research Consortium. Prevalence of SARS-CoV-2 Prevalence of SARS-CoV-2 infection among health care workers in a tertiary community hospital Pandemic peak SARS-CoV-2 infection and seroconversion rates in London frontline health-care workers SARS-CoV-2 antibody screening in healthcare workers in a tertiary centre in North West England Hospital-wide SARS-CoV-2 antibody screening in 3056 staff in a tertiary center in Belgium Large-scale, molecular and serological SARS-CoV-2 screening of healthcare workers in a 4-site public hospital in Belgium after COVID-19 outbreak Point-of-care serological assays for delayed SARS-CoV-2 case identification among health-care workers in the UK: a prospective multicentre cohort study Cumulative incidence and diagnosis of SARS-CoV-2 infection in New York Estimated community seroprevalence of SARS-CoV-2 antibodies -Two Georgia Counties Population point prevalence of SARS-CoV-2 infection based on a statewide random sample -Indiana SEROCoV-POP): a population-based study Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study Repeated leftover serosurvey of SARS-CoV-2 IgG antibodies China's practice to prevent and control COVID-19 in the context of large population movement Comparisons between countries are essential for the control of COVID-19 Covid-19 and the stiff upper lip-the pandemic response in the United Kingdom Facing Covid-19 in Italy-ethics, logistics, and therapeutics on the epidemic's front line Controlling SARS: a review on China's response compared with other SARS-affected countries Evaluation of control measures implemented in the severe acute respiratory syndrome outbreak in Beijing Reasons for healthcare workers becoming infected with novel coronavirus disease 2019 (COVID-19) in China Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study Predicting infectious SARS-CoV-2 from diagnostic samples Beyond the assistance: additional exposure situations to COVID-19 for healthcare workers COVID-19 in Australian healthcare workers: early experience of the Royal Melbourne Hospital emphasises the importance of community acquisition Epidemiological, clinical characteristics and outcome of medical staff infected with COVID-19 in Wuhan, China: a retrospective case series analysis Dissecting antibody-mediated protection against SARS Rapid point-of-care testing for SARS-CoV-2 in a community screening setting shows low sensitivity Dynamics and significance of the antibody response to SARS-CoV-2 infection The role of antibody testing for SARS-CoV-2: Is there one? Coronavirus disease 2019 case surveillance-United States Exclusive: deaths of NHS staff from COVID-19 analysed International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity Reference Factors investigated for SARS-CoV-2 antibodies positivity Factors associated with SARS-CoV-2 antibodies positivity Level of analysis Age, sex, race/ethnicity, borough/county of residence, type of occupation, previously diagnosed with COVID-19 by PCR test, self-reported high suspicion of SARS-CoV-2 exposure, primary location of clinical work, direct patient care Sex, ethnicity, type of occupation, primary location of clinical work None Univariate Steensels et al Age, sex, involvement in clinical care, work during the lockdown phase, involvement in care for COVID-19 patients, exposure to COVID-19 positive coworkers and household contact with suspected or confirmed COVID-19 patients -Household contact with suspected or confirmed COVID-19 patients Age, sex, type of occupation, level of exposure to COVID-19 patients Age, sex, type of occupation, level of exposure to COVID-19 patients Age, sex, type of occupation, level of exposure to COVID-19 patients Age, sex, type of occupation, primary location of clinical work -Surgery department (OR=6.47, 95% CI=2.37-17.63, p=0.0003) and pediatric intensive care unit Age, sex, race/ethnicity, chronic medical conditions, substance use, type of occupation, primary location of clinical work, participants' reported belief that (s)he previously had COVID-19, face covering for all clinical encounters is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 27, 2020.