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Background Cardiac troponins are the preferred biomarkers for the diagnosis of acute myocardial infarction. Although sex‐specific 99th percentile thresholds of troponins are recommended in international guidelines, the clinical effect of their use is poorly investigated. The DANSPOT Study (The Danish Study of Sex‐ and Population‐Specific 99th percentile upper reference limits of Troponin) aims to evaluate the clinical effect of a prospective implementation of population‐ and sex‐specific diagnostic thresholds of troponins into clinical practice. Methods This study is a nationwide, multicenter, stepped‐wedge cluster‐randomized trial of the implementation of population‐ and sex‐specific thresholds of troponins in 22 of 23 clinical centers in Denmark. We established sex‐specific thresholds for 5 different troponin assays based on troponin levels in a healthy Danish reference population. Centers will sequentially cross over from current uniform manufacturer‐derived thresholds to the new population‐ and sex‐specific thresholds. The primary cohort is defined as patients with symptoms suggestive of acute coronary syndrome having at least 1 troponin measurement performed within 24 hours of arrival with a peak troponin value between the current uniform threshold and the new sex‐specific female and male thresholds. The study will compare the occurrence of the primary outcome, defined as a composite of nonfatal myocardial infarction, unplanned revascularization, and all‐cause mortality within 1 year, separately for men and women before and after the implementation of the new sex‐specific thresholds. Conclusions The DANSPOT Study is expected to show the clinical effects on diagnostics, treatment, and clinical outcomes in patients with myocardial infarction of implementing sex‐specific diagnostic thresholds for troponin based on a national Danish reference population. Registration URL: https://www.clinicaltrials.gov; Unique identifier, BACKGROUND: Cardiac troponins are the preferred biomarkers for the diagnosis of acute myocardial infarction. Although sex-specific 99th percentile thresholds of troponins are recommended in international guidelines, the clinical effect of their use is poorly investigated. The DANSPOT Study (The Danish Study of Sex- and Population-Specific 99th percentile upper reference limits of Troponin) aims to evaluate the clinical effect of a prospective implementation of population- and sex-specific diagnostic thresholds of troponins into clinical practice. METHODS: This study is a nationwide, multicenter, stepped-wedge cluster-randomized trial of the implementation of population- and sex-specific thresholds of troponins in 22 of 23 clinical centers in Denmark. We established sex-specific thresholds for 5 different troponin assays based on troponin levels in a healthy Danish reference population. Centers will sequentially cross over from current uniform manufacturer-derived thresholds to the new population- and sex-specific thresholds. The primary cohort is defined as patients with symptoms suggestive of acute coronary syndrome having at least 1 troponin measurement performed within 24 hours of arrival with a peak troponin value between the current uniform threshold and the new sex-specific female and male thresholds. The study will compare the occurrence of the primary outcome, defined as a composite of nonfatal myocardial infarction, unplanned revascularization, and all-cause mortality within 1 year, separately for men and women before and after the implementation of the new sex-specific thresholds. CONCLUSIONS: The DANSPOT Study is expected to show the clinical effects on diagnostics, treatment, and clinical outcomes in patients with myocardial infarction of implementing sex-specific diagnostic thresholds for troponin based on a national Danish reference population. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT05336435.

To accommodate waning COVID-19 vaccine immunity to emerging SARS-CoV-2 variants, variant-adapted mRNA vaccines have been introduced. Here, we examine serological responses to the BA.1 and BA.4-5 Omicron variant-adapted BNT162b2 COVID-19 vaccines in people with lymphoid malignancies. We included 233 patients with lymphoid malignancies (chronic lymphocytic B-cell leukemia: 73 (31.3%), lymphoma: 89 (38.2%), multiple myeloma/amyloidosis: 71 (30.5%)), who received an Omicron-adapted mRNA-based COVID-19 vaccine. IgG and neutralizing antibodies specific for the receptor-binding domain (RBD) of SARS-CoV-2 were measured using ELISA-based methods. Differences in antibody concentrations and neutralizing capacity and associations with risk factors were assessed using mixed-effects models. Over the period of vaccination with an Omicron-adapted COVID-19 vaccine, the predicted mean concentration of anti-RBD IgG increased by 0.09 log10 AU/mL/month (95% CI: 0.07; 0.11) in patients with lymphoid malignancies across diagnoses. The predicted mean neutralizing capacity increased by 0.9 percent points/month (95% CI: 0.2; 1.6). We found no associations between the increase in antibody concentration or neutralizing capacity and the variant included in the adapted vaccine. In conclusion, a discrete increase in antibody concentrations and neutralizing capacity was found over the course of Omicron-adapted vaccination in patients with lymphoid malignancies regardless of the adapted vaccine variant, indicating a beneficial effect of Omicron-adapted booster vaccination in this population.

We investigated the humoral response to the Pfizer-BioNTech COVID-19 (BNT162b2) vaccine in patients with myasthenia gravis on or off immunosuppressants and compared this to the response in healthy individuals. The SARS-CoV-2 IgG response and neutralizing capacity were measured in 83 patients (57 on immunosuppressants) and 332 healthy controls at baseline, three weeks, and two and six months after the vaccine. We found that the proportion of positive humoral response was lower in patients on immunosuppressants vs. controls at three weeks and two months (p ≤ 0.001), but not at six months post-vaccination (p = 0.379)., We investigated the humoral response to the Pfizer-BioNTech COVID-19 (BNT162b2) vaccine in patients with myasthenia gravis on or off immunosuppressants and compared this to the response in healthy individuals. The SARS-CoV-2 IgG response and neutralizing capacity were measured in 83 patients (57 on immunosuppressants) and 332 healthy controls at baseline, three weeks, and two and six months after the vaccine. We found that the proportion of positive humoral response was lower in patients on immunosuppressants vs. controls at three weeks and two months (p ≤ 0.001), but not at six months post-vaccination (p = 0.379).

Troponin er førstevalg som biomarkør for akut myokardieinfarkt (AMI) [1]. Der er to hjertespecifikke isoformer af troponin, troponin I og T, som kan skelnes biokemisk fra troponin i skeletmuskel [1]. Den nyeste generation af højsensitive troponinassays er blevet indført løbende på danske hospitaler over de seneste 15 år. Med disse er det nu muligt at måle troponinniveauet i blodet på mere end 50% af raske personer og identificere små ændringer i cirkulerende troponinkoncentrationer [2]. Trods den høje specificitet forekommer forhøjede troponinmålinger uden hjertesygdom hyppigt [2]. De forhøjede målinger kan i denne sammenhæng skyldes myokardieskade eller analytisk interferens, hvor der måles en falsk forhøjet værdi pga. tekniske fejl i målingsmetoden. Man må få mistanke om analytisk interferens, når det kliniske billede ikke stemmer overens med den målte troponinkoncentration. I denne artikel opsummeres årsager til forhøjet troponinniveau med fokus på de nonkardiale årsager. Samtidig vil vi give et bud på, hvordan man kan håndtere udredningen af patienter, hos hvem der er en formodning om falsk forhøjede troponinmålinger., With the increased sensitivity of the newest cardiac troponin assays, the risk of false positive cardiac troponin measurements has also increased. As summarised in this review, there are multiple possible causes of cardiac troponin release including several non-cardiac illnesses, particularly kidney disease. Further, there is a risk of analytical interference in which case repeated measurements with a different assay is a good tool. When there is a discrepancy between troponin measurement and clinical presentation of the patient, the clinician should consider the possibility of analytical interference.

Knowledge about the effect of vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on immunity reflected in the saliva is sparse. We examined the antibody response in saliva compared to that in serum 2 and 6 months after the first vaccination with the BNT162b2 vaccine. Four hundred fifty-nine health care professionals were included in a prospective observational study measuring antibody levels in saliva and corresponding serum samples at 2 and 6 months after BNT162b2 vaccination. Vaccinated, previously SARS-CoV-2-infected individuals (hybrid immunity) had higher IgG levels in saliva at 2 months than vaccinated, infection-naive individuals (P , 0.001). After 6 months, saliva IgG levels declined in both groups (P , 0.001), with no difference between groups (P = 0.37). Furthermore, serum IgG levels declined from 2 to 6 months in both groups (P , 0.001). IgG antibodies in saliva and serum correlated in individuals with hybrid immunity at 2 and 6 months (r = 0.58, P = 0.001, and r = 0.53, P = 0.052, respectively). In vaccinated, infection-naive individuals, a correlation was observed at 2 months (r = 0.42, P , 0.001) but not after 6 months (r = 0.14, P = 0.055). IgA and IgM antibodies were hardly detectable in saliva at any time point, regardless of previous infection. In serum, IgA was detected at 2 months in previously infected individuals. BNT162b2 vaccination induced a detectable IgG anti-SARS-CoV-2 RBD response in saliva at both 2 and 6 months after vaccination, being more prominent in previously infected than infection-naive individuals. However, a significant decrease in salivary IgG was observed after 6 months, suggesting a rapid decline in antibody-mediated saliva immunity against SARS-CoV-2, after both infection and systemic vaccination. IMPORTANCE Knowledge about the persistence of salivary immunity after SARS-CoV-2 vaccination is limited, and information on this topic could prove important for vaccine strategy and development. W

Background and In the Partial Oral Treatment of Endocarditis (POET) trial, stabilized patients with left-sided infective endocarditis (IE) were Aims randomized to oral step-down antibiotic therapy (PO) or conventional continued intravenous antibiotic treatment (IV), showing non-inferiority after 6 months. In this study, the first guideline-driven clinical implementation of the oral step-down POET regimen was examined. Methods Patients with IE, caused by Staphylococcus aureus, Enterococcus faecalis, Streptococcus spp. or coagulase-negative staphylococci diagnosed between May 2019 and December 2020 were possible candidates for initiation of oral step-down antibiotic therapy, at the discretion of the treating physician. The composite primary outcome in patients finalizing antibiotic treatment consisted of embolic events, unplanned cardiac surgery, relapse of bacteraemia and all-cause mortality within 6 months. Results A total of 562 patients [median age 74 years (IQR, interquartile range, 65–80), 70% males] with IE were possible candidates; PO was given to 240 (43%) patients and IV to 322 (57%) patients. More patients in the IV group had IE caused by S. aureus, or had an intra-cardiac abscess, or a pacemaker and more were surgically treated. The primary outcome occurred in 30 (13%) patients in the PO group and in 59 (18%) patients in the IV group (P = .051); in the PO group, 20 (8%) patients died vs. 46 (14%) patients in the IV group (P = .024). PO-treated patients had a shorter median length of stay [PO 24 days (IQR 17–36) vs. IV 43 days (IQR 32–51), P < .001]. Conclusions After clinical implementation of the POET regimen almost half of the possible candidates with IE received oral step-down antibiotic therapy. Patients in the IV group had more serious risk factors for negative outcomes. At 6-month follow-up, there was a numerically but not statistically significant difference towards a lower incidence of the primary outcome, a lower incidence of all-cause morta

Guidelines do not differentiate between the available assays of cardiac troponin (cTn). We compared the prognostic and predictive ability of cTn assays, Aims Guidelines do not differentiate between the available assays of cardiac troponin (cTn). We compared the prognostic and predictive ability of cTn assays. Methods and results This was a nationwide cohort study of patients with acute coronary syndrome (ACS) and >= 2 cTn measurements of one of four assays: Roche high-sensitivity cTnT (hs-cTnT), Abbott high sensitivity cTnI (hs-cTnI), Siemens Vista cTnI, and Siemens cTnI Ultra. Data were collected from Danish registries from 2009-18. Peak cTn concentration normalized to the 99(th) percentile was used. Outcomes were myocardial infarction (MI) during admission, one-year all-cause-, cardiovascular-, and non-cardiovascular mortality. Receiver operating characteristics and logistic regression calculating odds ratios (OR) were used. A total of 90 705 patients were included, of which 20 550 (23%) had MI. Siemens Vista cTnI was the strongest predictor of MI, Area under the curve (auc) 0.93 (95% CI 0.93-0.93). In 1 year 9012 (9.9%) of patients had died. An inverted U-shape relationship was observed between concentration of cTn and all-cause mortality. Hs-cTnT OR 21.3 (95% CI 18.4-24.8) at 2-5 times the 99(th) percentile and 12.1 (95% CI 10.3-14.1) for concentrations >100 times the 99(th) percentile. The inverted U-shape relationship was only present for non-cardiovascular mortality. The strongest predictor of cardiovascular mortality was hs-cTnT, OR 11.3 (95% CI 6.4-21.8) at 1-2 times the 99(th) percentile and 88.8 (95% CI 53.2-163.0) for concentrations >100 times the 99(th) percentile. Conclusion Siemens Vista cTnI was the strongest predictor of MI and hs-cTnT was the strongest predictor of mortality. An inverted U-shape relationship was observed between cTn concentration and non-cardiovascular mortality.

Background: People with HIV (PWH) are at increased risk of severe COVID-19. We aimed to determine humoral responses in PWH and controls who received two doses of BNT162b2. Methods: In 269 PWH and 538 age-matched controls, we measured IgG and neutralizing antibodies specific for the receptor-binding domain of SARS-CoV-2 at baseline, 3 weeks and 2 months after the first dose of BNT162b2. Results: IgG antibodies increased from baseline to 3 weeks and from 3 weeks to 2 months in both groups, but the concentrations of IgG antibodies were lower in PWH than that in controls at 3 weeks and 2 months (p = 0.025 and <0.001), respectively. The IgG titres in PWH with a humoral response at 2 months were 77.9% (95% confidence interval [62.5%–97.0%], age- and sex-adjusted p = 0.027) of controls. Conclusions: Reduced IgG antibody response to vaccination with BNT162b2 was found in PWH, and thus increased awareness of breakthrough infections in PWH is needed.

OBJECTIVE: To assess the prevalence and severity of anaemia in patients with left-sided infective endocarditis (IE) and association with mortality. METHODS: In the Partial Oral versus Intravenous Antibiotic Treatment of Endocarditis trial, 400 patients with IE were randomised to conventional or partial oral antibiotic treatment after stabilisation of infection, showing non-inferiority. Haemoglobin (Hgb) levels were measured at randomisation. Primary outcomes were all-cause mortality after 6 months and 3 years. Patients who underwent valve surgery were excluded due to competing reasons for anaemia. RESULTS: Out of 400 patients with IE, 248 (mean age 70.6 years (SD 11.1), 62 women (25.0%)) were medically managed; 37 (14.9%) patients had no anaemia, 139 (56.1%) had mild anaemia (Hgb <8.1 mmol/L in men and Hgb <7.5 mmol/L in women and Hgb ≥6.2 mmol/L) and 72 (29.0%) had moderate to severe anaemia (Hgb <6.2 mmol/L). Mortality rates in patients with no anaemia, mild anaemia and moderate to severe anaemia were 2.7%, 3.6% and 15.3% at 6-month follow-up and 13.5%, 20.1% and 34.7% at 3-year follow-up, respectively. Moderate to severe anaemia was associated with higher mortality after 6 months (HR 4.81, 95% CI 1.78 to 13.0, p=0.002) and after 3 years (HR 2.14, 95% CI 1.27 to 3.60, p=0.004) and remained significant after multivariable adjustment. CONCLUSION: Moderate to severe anaemia was present in 29% of patients with medically treated IE after stabilisation of infection and was independently associated with higher mortality within the following 3 years. Further investigations are warranted to determine whether intensified treatment of anaemia in patients with IE might improve outcome.

Background The purpose of this study was to assess whether influenza vaccination has an impact on the risk of coronavirus disease 2019 (COVID-19). Methods A cohort of 46 112 healthcare workers were tested for antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and filled in a survey on COVID-19 symptoms, hospitalization, and influenza vaccination. Results The risk ratio of hospitalization due to SARS-CoV-2 for influenza vaccinated compared with unvaccinated participants was 1.00 for the seasonal vaccination in 2019/2020 (confidence interval, .56-1.78, P = 1.00). Likewise, no clinical effect of influenza vaccination on development of antibodies against SARS-CoV-2 was found. Conclusions The present findings indicate that influenza vaccination does not affect the risk of SARS-CoV-2 infection or COVID-19.This cohort study of 46 112 healthcare workers examined the effect of influenza vaccination on hospitalization and symptoms due to COVID-19 and development of antibodies against SARS-CoV-2. Influenza vaccination had no effect on the specified outcomes.

INTRODUCTION: Responses to COVID-19 vaccination in patients with chronic pulmonary diseases are poorly characterised. We aimed to describe humoral responses following two doses of BNT162b2 mRNA COVID-19 vaccine and identify risk factors for impaired responses.METHODS: Prospective cohort study including adults with chronic pulmonary diseases and healthcare personnel as controls (1:1). Blood was sampled at inclusion, 3 weeks, 2 and 6 months after first vaccination. We reported antibody concentrations as geometric means with 95% CI of receptor binding domain (RBD)-IgG and neutralising antibody index of inhibition of ACE-2/RBD interaction (%). A low responder was defined as neutralising index in the lowest quartile (primary outcome) or RBD-IgG <225 AU/mL plus neutralising index <25% (secondary outcome), measured at 2 months. We tested associations using Poisson regression.RESULTS: We included 593 patients and 593 controls, 75% of all had neutralising index ≥97% at 2 months. For the primary outcome, 34.7% of patients (n=157/453) and 12.9% of controls (n=46/359) were low responders (p<0.0001). For the secondary outcome, 8.6% of patients (n=39/453) and 1.4% of controls (n=5/359) were low responders (p<0.001). Risk factors associated with low responder included increasing age (per decade, adjusted risk ratio (aRR) 1.17, 95% CI 1.03 to 1.32), Charlson Comorbidity Index (per point) (aRR 1.15, 95% CI 1.05 to 1.26), use of prednisolone (aRR 2.08, 95% CI 1.55 to 2.77) and other immunosuppressives (aRR 2.21, 95% CI 1.65 to 2.97).DISCUSSION: Patients with chronic pulmonary diseases established functional humoral responses to vaccination, however lower than controls. Age, comorbidities and immunosuppression were associated with poor immunological responses.

Background Cardiac Troponin (cTn) is the biochemical gold standard for diagnosing myocardial infarction (MI). We compared the Siemens ADVIA Centaur high-sensitivity (hs-cTnI) assay with the Siemens Ultra assay (cTnI-U). Methods Over 3 months cTnI-U and hs-cTnI were measured simultaneously at Herlev-Gentofte Hospital. Acute myocardial injury was diagnosed using the 4th universal definition. Disputed cases were adjudicated using clinical data. We compared diagnostic accuracy using area under the curve (AUC) of the receiver operating characteristic. Outliers in between-assay differences were defined as a factor-5 difference and >= 1 measurement >40 ng/L. Patients with outlier differences were invited for re-sampling and tested with serial dilution and heterophilic blocking tubes. Results From the 18th January to the 20th April 2019, 4,369 samples on 2,658 patients were included. cTnI-U measured higher concentrations than hs-cTnI (mean 23%, -52-213%), resulting in a higher frequency of acute myocardial injury, 255 (9.6%) vs 203 (7.6%), p

In this study of 1 549 488 individuals in the Capital Region of Denmark, of which 1 119 574 were vaccinated against SARS-CoV-2, we found that individuals who received 2 doses of a COVID-19 vaccine had very low risk of breakthrough infections with SARS-CoV-2.Background Coronavirus disease 2019 (COVID-19) vaccines are implemented worldwide in efforts to curb the pandemic. This study investigates the risk of a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcriptase polymerase chain reaction (RT-PCR) test following BNT162b2 vaccination in a large real-life population in Denmark. Methods Vaccination status and positive SARS-CoV-2 RT-PCR results from adults in the Capital Region of Denmark (n = 1 549 488) were obtained from national registries. PCR testing was free and widely available. The number of positive PCR tests per individual at risk was calculated as weekly rates. Time to positive PCR test was modelled using Kaplan-Meier methods and hazard ratios (HRs) were calculated using Cox regression. Results A total of 1 119 574 individuals received the first dose of BNT162b2 and 1 088 879 received a second dose of BNT162b2. Individuals were followed up to 8.7 months after first dose (median: 5.5 months; interquartile ratio: 4.1-8.7). Rates of PCR-confirmed SARS-CoV-2 infection 2-4 months after the second dose were 0.21, 0.33, and 0.36 per 1000 individuals per week at risk for July, August, and September, respectively. Four or more months after the second dose, the rates were 0.56, 0.76, and 0.53 per 1000 individuals per week at risk for July, August, and September, respectively. HR of SARS-CoV-2 infection after the second dose was 0.2 (95% confidence interval, .05-.48; P = .001) for individuals with 8 months' follow-up. Conclusions Individuals who received 2 doses of the BNT162b2 COVID-19 vaccine had a low risk of breakthrough infection after up to 8 months of follow-up. However, there was a tendency toward higher rates with lo

Background: Previous studies have indicated inferior responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccination in solid organ transplant (SOT) recipients. We examined the development of anti-receptor-binding domain (RBD) immunoglobulin G (IgG) after two doses of BNT162b2b in SOT recipients 6 months after vaccination and compared to that of immunocompetent controls. Methods: We measured anti-RBD IgG after two doses of BNT162b2 in 200 SOT recipients and 200 matched healthy controls up to 6 months after first vaccination. Anti-RBD IgG concentration and neutralizing capacity of antibodies were measured at first and second doses of BNT162b2 and 2 and 6 months after the first dose. T-cell responses were measured 6 months after the first dose. Results: In SOT recipients, geometric mean concentration (GMC) of anti-RBD IgG increased from first to second dose (1.14 AU/ml, 95% CI 1.08-1.24 to 11.97 AU/ml, 95% CI 7.73-18.77) and from second dose to 2 months (249.29 AU/ml, 95% CI 153.70-385.19). Six months after the first vaccine, anti-RBD IgG declined (55.85 AU/ml, 95% CI 36.95-83.33). At all time points, anti-RBD IgG was lower in SOT recipients than that in controls. Fewer SOT recipients than controls had a cellular response (13.1% vs. 59.4%, p < 0.001). Risk factors associated with humoral non-response included age [relative risk (RR) 1.23 per 10-year increase, 95% CI 1.11-1.35, p < 0.001], being within 1 year from transplantation (RR 1.55, 95% CI 1.30-1.85, p < 0.001), treatment with mycophenolate (RR 1.54, 95% CI 1.09-2.18, p = 0.015), treatment with corticosteroids (RR 1.45, 95% CI 1.10-1.90, p = 0.009), kidney transplantation (RR 1.70, 95% CI 1.25-2.30, p = 0.001), lung transplantation (RR 1.63, 95% CI 1.16-2.29, p = 0.005), and de novo non-skin cancer comorbidity (RR 1.52, 95% CI, 1.26-1.82, p < 0.001). Conclusion: Immune responses to BNT162b2 are inferior in SOT recipients compared to healthy controls, and studies aiming to det

Objectives: Antibodies to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are a key factor in protecting against coronavirus disease 2019 (COVID-19). We examined longitudinal changes in seroprevalence in healthcare workers (HCWs) in Copenhagen and the protective effect of antibodies against SARS-CoV-2. Methods: In this prospective study, screening for antibodies against SARS-CoV-2 (ELISA) was offered to HCWs three times over 6 months. HCW characteristics were obtained by questionnaires. The study was registered at ClinicalTrials.gov, NCT04346186. Results: From April to October 2020 we screened 44 698 HCWs, of whom 2811 were seropositive at least once. The seroprevalence increased from 4.0% (1501/37 452) to 7.4% (2022/27 457) during the period (p < 0.001) and was significantly higher than in non-HCWs. Frontline HCWs had a significantly increased risk of seropositivity compared to non-frontline HCWs, with risk ratios (RRs) at the three rounds of 1.49 (95%CI 1.34–1.65, p < 0.001), 1.52 (1.39–1.68, p < 0.001) and 1.50 (1.38–1.64, p < 0.001). The seroprevalence was 1.42- to 2.25-fold higher (p < 0.001) in HCWs from dedicated COVID-19 wards than in other frontline HCWs. Seropositive HCWs had an RR of 0.35 (0.15–0.85, p 0.012) of reinfection during the following 6 months, and 2115 out of 2248 (95%) of those who were seropositive during rounds one or two remained seropositive after 4–6 months. The 133 of 2248 participants (5.0%) who seroreverted were slightly older and reported fewer symptoms than other seropositive participants. Conclusions: HCWs remained at increased risk of infection with SARS-CoV-2 during the 6-month period. Seropositivity against SARS-CoV-2 persisted for at least 6 months in the vast majority of HCWs and was associated with a significantly lower risk of reinfection.