Managing differential performance of polygenic risk scores across groups: Real-world experience of the eMERGE Network.

The differential performance of polygenic risk scores (PRSs) by group is one of the major ethical barriers to their clinical use. It is also one of the main practical challenges for any implementation effort. The social repercussions of how people are grouped in PRS research must be considered in communications with research participants, including return of results. Here, we outline the decisions faced and choices made by a large multi-site clinical implementation study returning PRSs to diverse participants in handling this issue of differential performance. Our approach to managing the complexities associated with the differential performance of PRSs serves as a case study that can help future implementers of PRSs to plot an anticipatory course in response to this issue.

Heart Failure Risk Among African-American Women With an ICAM1 Missense Variant.

BACKGROUND: A common genetic variant of ICAM1 among African-American individuals (rs5491; p.K56M) is associated with heart failure (HF) hospitalization, but whether this risk is specific to heart failure with preserved ejection fraction (HFpEF) remains unclear. Older women are at high risk for HFpEF, and the relationship between rs5491 and HFpEF across the age spectrum is unknown. OBJECTIVES: This study assessed risk of HF and its subtypes conferred by ICAM1 p.K56M (rs5491). METHODS: Associations of rs5491 with risk of HF and its subtypes were estimated among African American individuals in WHI (Women's Health Initiative). The study evaluated whether the association between rs5491 and HF hospitalizations was modified by baseline age. Subsequently, African-American women in WHI and MESA (Multi-Ethnic Study of Atherosclerosis) were pooled and analyses were repeated. RESULTS: Among 8,401 women in WHI, the minor allele frequency of rs5491 was 20.7%, and 731 HF hospitalizations occurred over 19.2 years. The rs5491 variant was not associated with HF or its subtypes across WHI. Interaction analyses suggested that age as a continuous variable modified the association of rs5491 with HFpEF hospitalization (interaction P = 0.04). Upon categorizing women into age decades, rs5491 conferred increased risk of HFpEF among women ≥70 years (HR per additional rs5491 allele: 1.82 [95% CI: 1.25-2.65]; P = 0.002) but was not associated with HFpEF risk among women <70 years. Pooling African-American women in WHI (n = 8,401) and MESA (n = 856) demonstrated that the effect modification by age on the association of rs5491 with HFpEF became more significant (interaction P = 0.009), with consistent HFpEF risk effect estimates among women ≥70 years. CONCLUSIONS: ICAM1 p.K56M (rs5491) is associated with HFpEF among African-American women ≥70 years.

Prospective, multi-site study of healthcare utilization after actionable monogenic findings from clinical sequencing.

As large-scale genomic screening becomes increasingly prevalent, understanding the influence of actionable results on healthcare utilization is key to estimating the potential long-term clinical impact. The eMERGE network sequenced individuals for actionable genes in multiple genetic conditions and returned results to individuals, providers, and the electronic health record. Differences in recommended health services (laboratory, imaging, and procedural testing) delivered within 12 months of return were compared among individuals with pathogenic or likely pathogenic (P/LP) findings to matched individuals with negative findings before and after return of results. Of 16,218 adults, 477 unselected individuals were found to have a monogenic risk for arrhythmia (n = 95), breast cancer (n = 96), cardiomyopathy (n = 95), colorectal cancer (n = 105), or familial hypercholesterolemia (n = 86). Individuals with P/LP results more frequently received services after return (43.8%) compared to before return (25.6%) of results and compared to individuals with negative findings (24.9%; p < 0.0001). The annual cost of qualifying healthcare services increased from an average of $162 before return to $343 after return of results among the P/LP group (p < 0.0001); differences in the negative group were non-significant. The mean difference-in-differences was $149 (p < 0.0001), which describes the increased cost within the P/LP group corrected for cost changes in the negative group. When stratified by individual conditions, significant cost differences were observed for arrhythmia, breast cancer, and cardiomyopathy. In conclusion, less than half of individuals received billed health services after monogenic return, which modestly increased healthcare costs for payors in the year following return.

Multi-ancestry genome- and phenome-wide association studies of diverticular disease in electronic health records with natural language processing enriched phenotyping algorithm.

OBJECTIVE: Diverticular disease (DD) is one of the most prevalent conditions encountered by gastroenterologists, affecting ~50% of Americans before the age of 60. Our aim was to identify genetic risk variants and clinical phenotypes associated with DD, leveraging multiple electronic health record (EHR) data sources of 91,166 multi-ancestry participants with a Natural Language Processing (NLP) technique. MATERIALS AND METHODS: We developed a NLP-enriched phenotyping algorithm that incorporated colonoscopy or abdominal imaging reports to identify patients with diverticulosis and diverticulitis from multicenter EHRs. We performed genome-wide association studies (GWAS) of DD in European, African and multi-ancestry participants, followed by phenome-wide association studies (PheWAS) of the risk variants to identify their potential comorbid/pleiotropic effects in clinical phenotypes. RESULTS: Our developed algorithm showed a significant improvement in patient classification performance for DD analysis (algorithm PPVs ≥ 0.94), with up to a 3.5 fold increase in terms of the number of identified patients than the traditional method. Ancestry-stratified analyses of diverticulosis and diverticulitis of the identified subjects replicated the well-established associations between ARHGAP15 loci with DD, showing overall intensified GWAS signals in diverticulitis patients compared to diverticulosis patients. Our PheWAS analyses identified significant associations between the DD GWAS variants and circulatory system, genitourinary, and neoplastic EHR phenotypes. DISCUSSION: As the first multi-ancestry GWAS-PheWAS study, we showcased that heterogenous EHR data can be mapped through an integrative analytical pipeline and reveal significant genotype-phenotype associations with clinical interpretation. CONCLUSION: A systematic framework to process unstructured EHR data with NLP could advance a deep and scalable phenotyping for better patient identification and facilitate etiological investigation of a disease with multilayered data.

Causal effects on complex traits are similar for common variants across segments of different continental ancestries within admixed individuals.

Individuals of admixed ancestries (for example, African Americans) inherit a mosaic of ancestry segments (local ancestry) originating from multiple continental ancestral populations. This offers the unique opportunity of investigating the similarity of genetic effects on traits across ancestries within the same population. Here we introduce an approach to estimate correlation of causal genetic effects (radmix) across local ancestries and analyze 38 complex traits in African-European admixed individuals (N = 53,001) to observe very high correlations (meta-analysis radmix = 0.95, 95% credible interval 0.93-0.97), much higher than correlation of causal effects across continental ancestries. We replicate our results using regression-based methods from marginal genome-wide association study summary statistics. We also report realistic scenarios where regression-based methods yield inflated heterogeneity-by-ancestry due to ancestry-specific tagging of causal effects, and/or polygenicity. Our results motivate genetic analyses that assume minimal heterogeneity in causal effects by ancestry, with implications for the inclusion of ancestry-diverse individuals in studies.

Investigating Gene-Diet Interactions Impacting the Association Between Macronutrient Intake and Glycemic Traits.

Few studies have demonstrated reproducible gene-diet interactions (GDIs) impacting metabolic disease risk factors, likely due in part to measurement error in dietary intake estimation and insufficient capture of rare genetic variation. We aimed to identify GDIs across the genetic frequency spectrum impacting the macronutrient-glycemia relationship in genetically and culturally diverse cohorts. We analyzed 33,187 participants free of diabetes from 10 National Heart, Lung, and Blood Institute Trans-Omics for Precision Medicine program cohorts with whole-genome sequencing, self-reported diet, and glycemic trait data. We fit cohort-specific, multivariable-adjusted linear mixed models for the effect of diet, modeled as an isocaloric substitution of carbohydrate for fat, and its interactions with common and rare variants genome-wide. In main effect meta-analyses, participants consuming more carbohydrate had modestly lower glycemic trait values (e.g., for glycated hemoglobin [HbA1c], -0.013% HbA1c/250 kcal substitution). In GDI meta-analyses, a common African ancestry-enriched variant (rs79762542) reached study-wide significance and replicated in the UK Biobank cohort, indicating a negative carbohydrate-HbA1c association among major allele homozygotes only. Simulations revealed that >150,000 samples may be necessary to identify similar macronutrient GDIs under realistic assumptions about effect size and measurement error. These results generate hypotheses for further exploration of modifiable metabolic disease risk in additional cohorts with African ancestry. ARTICLE HIGHLIGHTS: We aimed to identify genetic modifiers of the dietary macronutrient-glycemia relationship using whole-genome sequence data from 10 Trans-Omics for Precision Medicine program cohorts. Substitution models indicated a modest reduction in glycemia associated with an increase in dietary carbohydrate at the expense of fat. Genome-wide interaction analysis identified one African ancestry-enriched variant near the FRAS1 gene that may interact with macronutrient intake to influence hemoglobin A1c. Simulation-based power calculations accounting for measurement error suggested that substantially larger sample sizes may be necessary to discover further gene-macronutrient interactions.

Secretory leukocyte protease inhibitor and risk of heart failure in the Multi-Ethnic Study of Atherosclerosis.

Circulating protease inhibitors are important regulators of inflammation that are implicated in the pathophysiology of heart failure (HF). Secretory leukocyte protease inhibitor (SLPI) is a serine protease inhibitor which protects pulmonary tissues against inflammatory damage; however, its role in HF is not well understood. We sought to evaluate associations of circulating SLPI and genetically-mediated serum SLPI with incident HF and its subtypes in a multi-ethnic cohort of adults using clinical and genetic epidemiological approaches. Among 2,297 participants in the Multi-Ethnic Study of Atherosclerosis (MESA), each doubling of serum SLPI was independently associated with incident HF (HR 1.77; 95% CI 1.02-3.02; P = 0.04), particularly incident HF with preserved ejection fraction (HFpEF; HR 2.44; 95% CI 1.23-4.84; P = 0.01) but not HF with reduced ejection fraction (HFrEF; HR 0.95; 95% CI 0.36-2.46; P = 0.91). Previously reported circulating SLPI protein quantitative trait loci (pQTLs) were not associated with serum SLPI levels or incident HF among MESA participants. In conclusion, baseline serum SLPI levels, but not genetically-determined serum SLPI, were significantly associated with incident HF and HFpEF over long-term follow-up in a multi-ethnic cohort. Serum circulating SLPI may be a correlate of inflammation that sheds insight on the pathobiology of HFpEF.

Genome-wide association and multi-trait analyses characterize the common genetic architecture of heart failure.

Heart failure is a leading cause of cardiovascular morbidity and mortality. However, the contribution of common genetic variation to heart failure risk has not been fully elucidated, particularly in comparison to other common cardiometabolic traits. We report a multi-ancestry genome-wide association study meta-analysis of all-cause heart failure including up to 115,150 cases and 1,550,331 controls of diverse genetic ancestry, identifying 47 risk loci. We also perform multivariate genome-wide association studies that integrate heart failure with related cardiac magnetic resonance imaging endophenotypes, identifying 61 risk loci. Gene-prioritization analyses including colocalization and transcriptome-wide association studies identify known and previously unreported candidate cardiomyopathy genes and cellular processes, which we validate in gene-expression profiling of failing and healthy human hearts. Colocalization, gene expression profiling, and Mendelian randomization provide convergent evidence for the roles of BCKDHA and circulating branch-chain amino acids in heart failure and cardiac structure. Finally, proteome-wide Mendelian randomization identifies 9 circulating proteins associated with heart failure or quantitative imaging traits. These analyses highlight similarities and differences among heart failure and associated cardiovascular imaging endophenotypes, implicate common genetic variation in the pathogenesis of heart failure, and identify circulating proteins that may represent cardiomyopathy treatment targets.

Trajectories of Depressive and Anxiety Symptoms Across Pregnancy and Postpartum in Selective Serotonin Reuptake Inhibitor-Treated Women.

Objective: Tracking perinatal mood and anxiety disorders is championed by the American Psychiatric Association and the International Marcé Society for Perinatal Mental Health. We conducted this study to examine trajectories of monthly depressive and anxiety symptoms through pregnancy and postpartum. Methods: This is a prospective longitudinal observational cohort study of pregnant women interviewed at baseline (≤18th gestational week), every four weeks through delivery and at 6 and 14 weeks postpartum at three urban academic medical centers (N = 85) and a single rural health center (N = 3) from 2016 to 2020. Pregnant women had at least one prior episode of major depressive disorder, were not in a current episode, and were treated with sertraline, fluoxetine, citalopram, or escitalopram. Of 192 women screened, 88 (46%) women enrolled, and 77 (88%) women completed the postpartum follow-up. Symptom trajectories were generated with scores from the Edinburgh Postnatal Depression Scale, the Quick Inventory of Depressive Symptoms, the Generalized Anxiety Disorder Scale, 7-item, and the Patient-Reported Outcomes Measurement Information System Global Health measure. A semi-parametric, group-based mixture model (trajectory analysis) was applied. Results: Three relatively stable depression trajectories emerged, described as Minimal, Mild, and Subthreshold, in each group across pregnancy. Two of the four anxiety trajectories were stable, including Asymptomatic and Minimal, while the third, termed Breakthrough, was ascending with increasing symptoms and the fourth trajectory, described as Mild, had descending symptoms. Conclusions: Screening for anxiety with depression for pregnant women will yield a comprehensive view of psychiatric symptoms and treatment targets in perinatal women.

Changes in Sertraline Plasma Concentrations Across Pregnancy and Postpartum.

Major depressive disorder (MDD) is a common disorder in pregnancy. Although sertraline is the most frequently prescribed antidepressant for pregnant people in the United States, limited information about its pharmacokinetics in pregnancy is available. Our objectives were to characterize plasma sertraline concentration to dose (C/D) ratios across pregnancy and postpartum and investigate the effect of pharmacogenetic variability on sertraline elimination. We performed a prospective observational cohort study in people with a singleton pregnancy ≤ 18 weeks gestation and a lifetime diagnosis of MDD at the 3 Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)-funded Obstetrical-Fetal Pharmacology Research Center sites. Subjects (N = 47) were receiving maintenance sertraline therapy and chose to continue it during pregnancy. Blood samples were obtained 24-hours postdose every 4 weeks across pregnancy and twice postpartum for measurement of plasma concentrations of sertraline and desmethylsertraline. Overall mean sertraline C/D ratios were decreased at study onset and remained consistently low until after delivery. During the last 4 weeks of pregnancy the mean sertraline C/D ratio (95% confidence interval (CI)), 0.25 (95% CI, 0.19, 0.3) ng/mL/dose (mg/day), was smaller than the mean ratio at ≥ 8 weeks after delivery, 0.32 (95% CI, 0.27, 0.37) ng/mL/dose (mg/day), a 22% difference. Mean sertraline/desmethylsertraline ratios were highest after birth, which confirmed increased sertraline elimination during pregnancy. Sertraline C/D ratios in participants with functional CYP2C19 activity did not change significantly during pregnancy, whereas ratios in participants with poor or intermediate CYP2C19 activity decreased by 51%. Exploratory pharmacogenomic analysis indicated that pregnant people with poor or intermediate CYP2C19 activity are at risk for subtherapeutic sertraline concentrations during pregnancy.

Whole genome sequence association analysis of fasting glucose and fasting insulin levels in diverse cohorts from the NHLBI TOPMed program.

The genetic determinants of fasting glucose (FG) and fasting insulin (FI) have been studied mostly through genome arrays, resulting in over 100 associated variants. We extended this work with high-coverage whole genome sequencing analyses from fifteen cohorts in NHLBI's Trans-Omics for Precision Medicine (TOPMed) program. Over 23,000 non-diabetic individuals from five race-ethnicities/populations (African, Asian, European, Hispanic and Samoan) were included. Eight variants were significantly associated with FG or FI across previously identified regions MTNR1B, G6PC2, GCK, GCKR and FOXA2. We additionally characterize suggestive associations with FG or FI near previously identified SLC30A8, TCF7L2, and ADCY5 regions as well as APOB, PTPRT, and ROBO1. Functional annotation resources including the Diabetes Epigenome Atlas were compiled for each signal (chromatin states, annotation principal components, and others) to elucidate variant-to-function hypotheses. We provide a catalog of nucleotide-resolution genomic variation spanning intergenic and intronic regions creating a foundation for future sequencing-based investigations of glycemic traits.

Large-scale genomic analyses reveal insights into pleiotropy across circulatory system diseases and nervous system disorders.

Clinical and epidemiological studies have shown that circulatory system diseases and nervous system disorders often co-occur in patients. However, genetic susceptibility factors shared between these disease categories remain largely unknown. Here, we characterized pleiotropy across 107 circulatory system and 40 nervous system traits using an ensemble of methods in the eMERGE Network and UK Biobank. Using a formal test of pleiotropy, five genomic loci demonstrated statistically significant evidence of pleiotropy. We observed region-specific patterns of direction of genetic effects for the two disease categories, suggesting potential antagonistic and synergistic pleiotropy. Our findings provide insights into the relationship between circulatory system diseases and nervous system disorders which can provide context for future prevention and treatment strategies.

Development and validation of a trans-ancestry polygenic risk score for type 2 diabetes in diverse populations.

BACKGROUND: Type 2 diabetes (T2D) is a worldwide scourge caused by both genetic and environmental risk factors that disproportionately afflicts communities of color. Leveraging existing large-scale genome-wide association studies (GWAS), polygenic risk scores (PRS) have shown promise to complement established clinical risk factors and intervention paradigms, and improve early diagnosis and prevention of T2D. However, to date, T2D PRS have been most widely developed and validated in individuals of European descent. Comprehensive assessment of T2D PRS in non-European populations is critical for equitable deployment of PRS to clinical practice that benefits global populations. METHODS: We integrated T2D GWAS in European, African, and East Asian populations to construct a trans-ancestry T2D PRS using a newly developed Bayesian polygenic modeling method, and assessed the prediction accuracy of the PRS in the multi-ethnic Electronic Medical Records and Genomics (eMERGE) study (11,945 cases; 57,694 controls), four Black cohorts (5137 cases; 9657 controls), and the Taiwan Biobank (4570 cases; 84,996 controls). We additionally evaluated a post hoc ancestry adjustment method that can express the polygenic risk on the same scale across ancestrally diverse individuals and facilitate the clinical implementation of the PRS in prospective cohorts. RESULTS: The trans-ancestry PRS was significantly associated with T2D status across the ancestral groups examined. The top 2% of the PRS distribution can identify individuals with an approximately 2.5-4.5-fold of increase in T2D risk, which corresponds to the increased risk of T2D for first-degree relatives. The post hoc ancestry adjustment method eliminated major distributional differences in the PRS across ancestries without compromising its predictive performance. CONCLUSIONS: By integrating T2D GWAS from multiple populations, we developed and validated a trans-ancestry PRS, and demonstrated its potential as a meaningful index of risk among diverse patients in clinical settings. Our efforts represent the first step towards the implementation of the T2D PRS into routine healthcare.

Practitioners' Confidence and Desires for Education in Cardiovascular and Sudden Cardiac Death Genetics.

Background Educating cardiologists and health care professionals about cardiovascular genetics and genetic testing is essential to improving diagnosis and management of patients with inherited cardiomyopathies and arrhythmias and those at higher risk for sudden cardiac death. The aim of this study was to understand cardiology and electrophysiology practitioners' current practices, confidence, and knowledge surrounding genetic testing in cardiology and desired topics for an educational program. Methods and Results A one-time survey was administered through purposive email solicitation to 131 cardiology practitioners in the United States. Of these, 107 self-identified as nongenetic practitioners. Over three quarters of nongenetic practitioners reported that they refer patients to genetic providers to discuss cardiovascular genetic tests (n=82; 76.6%). More than half of nongenetic practitioners reported that they were not confident about the types of cardiovascular genetic testing available (n=60; 56%) and/or in ordering appropriate cardiovascular genetic tests (n=66; 62%). In addition, 45% (n=22) of nongenetic practitioners did not feel confident making cardiology treatment recommendations based on genetic test results. Among all providers, the most desired topics for an educational program were risk assessment (94%) and management of inherited cardiac conditions based on guidelines (91%). Conclusions This study emphasizes the importance of access to genetics services in the cardiology field and the need for addressing the identified deficit in confidence and knowledge about cardiogenetics and genetic testing among nongenetic providers. Additional research is needed, including more practitioners from underserved areas.

Integrating clinical genetics in cardiology: Current practices and recommendations for education.

PURPOSE: Recent advances in genetics can facilitate the identification of at-risk individuals and diagnosis of cardiovascular disorders. As a nascent field, more research is needed to optimize the clinical practice of cardiovascular genetics, including the assessment of educational needs to promote appropriate use of genetic testing. METHODS: Qualitative interviews conducted with cardiovascular specialists (N = 43) were audiotaped. Thematic analysis was conducted on professional transcripts. RESULTS: Participants recognized the value of genetics in identifying and diagnosing at-risk individuals. However, organizational systems, cost, and feeling of unpreparedness were identified as barriers. Participants felt that the rapid pace of genetic science resulted in further challenges to maintaining an adequate knowledge base and highlighted genetics experts' importance. Even when a genetics expert was available, participants wanted to know more about which patients benefit most from genetic testing and expressed a desire to better understand management recommendations associated with a positive test result. CONCLUSION: Participants recognized the benefit but felt underprepared to provide recommendations for genetic testing and, in some cases, lacked organizational resources to refer patients to a genetics expert. Additional training in genetics for cardiology practitioners and ensuring availability of a genetics expert can improve the use of genetics in cardiology settings.

Genetic variation in sodium glucose co-transporter 1 and cardiac structure and function at middle age.

AIMS: The effects of inhibition of sodium glucose cotransporter (SGLT)-1, as opposed to SGLT2, on cardiovascular structure and function are not well known. We assessed the associations of a missense genetic variant of SGLT1 with cardiac structure and function. METHODS AND RESULTS: We evaluated associations of a functionally modifying variant of SLC5A1 (rs17683011 [p.Asn51Ser]), the gene that encodes SGLT1, with cardiac structure and function on echocardiography among middle-aged adults in the Coronary Artery Risk Development in Young Adults Study. Of 1904 participants (55.3 ± 3.5 years, 57% female, 34% Black), 166 (13%) White participants and 18 (3%) Black participants had at least one copy of rs17683011. There were no significant differences in age, sex, body mass index, glucose, or diabetes status by the presence of the rs17683011 variant. In Black participants, the presence of at least one copy of the rs17683011 variant was significantly associated with better GLS compared with those without a copy of the variant after covariate adjustment (-15.8 ± 0.7% vs. -14.0 ± 0.1%, P = 0.02). Although the direction of effect was consistent, the association between the presence of at least one copy of rs17683011 and GLS was not statistically significant in White participants (-15.1 ± 0.2% vs. -14.8 ± 0.1%, P = 0.16). There were no significant associations between rs17683011 and other measures of LV structure, systolic function, or diastolic function. CONCLUSIONS: The rs17683011 variant, a functionally modifying variant of the SGLT1 gene, was associated with higher GLS among middle-age adults. These exploratory findings require further validation and suggest that SGLT1 inhibition may have beneficial effects upon LV systolic function.

Validation of Heart Failure-Specific Risk Equations in 1.3 Million Israeli Adults and Usefulness of Combining Ambulatory and Hospitalization Data from a Large Integrated Health Care Organization.

Heart failure (HF) prevalence is increasing worldwide and is associated with significant morbidity and mortality. Guidelines emphasize prevention in those at-risk, but HF-specific risk prediction equations developed in United States population-based cohorts lack external validation in large, real-world datasets outside of the United States. The purpose of this study was to assess the model performance of the pooled cohort equations to prevent HF (PCP-HF) within a contemporary electronic health record for 5- and 10-year risk. Using a retrospective cohort study design of Israeli residents between 2008 and 2018 with continuous membership until end of follow-up, HF, or death, we quantified 5- and 10-year estimated risks of HF using the PCP-HF equations, which integrate demographics (age, gender, and race) and risk factors (body mass index, systolic blood pressure, glucose, medication use for hypertension or diabetes, and smoking status). Of 1,394,411 patients included, 56% were women with mean age of 49.6 (SD 13.2) years. Incident HF occurred in 1.2% and 4.5% of participants over 5 and 10 years of follow-up. The PCP-HF model had excellent discrimination for 5- and 10-year predictions of incident HF (C Statistic 0.82 [0.82 to 0.82] and 0.84 [0.84 to 0.84]), respectively. In conclusion, HF-specific risk equations (PCP-HF) accurately predict the risk of incident HF in ambulatory and hospitalized patients using routinely available clinical data.

Serologic Status and SARS-CoV-2 Infection over 6 Months of Follow Up in Healthcare Workers in Chicago: A Cohort Study.

OBJECTIVE: To determine the changes in severe acute respiratory coronavirus virus 2 (SARS-CoV-2) serologic status and SARS-CoV-2 infection rates in healthcare workers (HCWs) over 6-months of follow-up. DESIGN: Prospective cohort study. SETTING AND PARTICIPANTS: HCWs in the Chicago area. METHODS: Cohort participants were recruited in May and June 2020 for baseline serology testing (Abbott anti-nucleocapsid IgG) and were then invited for follow-up serology testing 6 months later. Participants completed monthly online surveys that assessed demographics, medical history, coronavirus disease 2019 (COVID-19), and exposures to SARS-CoV-2. The electronic medical record was used to identify SARS-CoV-2 polymerase chain reaction (PCR) positivity during follow-up. Serologic conversion and SARS-CoV-2 infection or possible reinfection rates (cases per 10,000 person days) by antibody status at baseline and follow-up were assessed. RESULTS: In total, 6,510 HCWs were followed for a total of 1,285,395 person days (median follow-up, 216 days). For participants who had baseline and follow-up serology checked, 285 (6.1%) of the 4,681 seronegative participants at baseline seroconverted to positive at follow-up; 138 (48%) of the 263 who were seropositive at baseline were seronegative at follow-up. When analyzed by baseline serostatus alone, 519 (8.4%) of 6,194 baseline seronegative participants had a positive PCR after baseline serology testing (4.25 per 10,000 person days). Of 316 participants who were seropositive at baseline, 8 (2.5%) met criteria for possible SARS-CoV-2 reinfection (ie, PCR positive >90 days after baseline serology) during follow-up, a rate of 1.27 per 10,000 days at risk. The adjusted rate ratio for possible reinfection in baseline seropositive compared to infection in baseline seronegative participants was 0.26 (95% confidence interval, 0.13-0.53). CONCLUSIONS: Seropositivity in HCWs is associated with moderate protection from future SARS-CoV-2 infection.