Introduction There is an increased risk of thrombotic complications in patients with COVID‐19. Hemodialysis patients are already at an increased risk for thromboembolic events such as stroke and pulmonary embolism. The aim of our study was to determine the incidence of late thrombotic complications (deep vein thrombosis, pulmonary embolism, stroke, new‐onset vascular access thrombosis) in maintenance hemodialysis patients after recovery from COVID‐19. Methods We performed a retrospective cohort study of 200 prevalent hemodialysis patients in our center at the start of the pandemic. We excluded incident patients after the cohort entry date and those who required hemodialysis for acute kidney injury, and excluded patients with less than 1 month follow‐up due to kidney transplantation or death from non‐thrombotic causes. Findings One‐hundred and eighty five prevalent hemodialysis patients finally met the inclusion criteria; 37 patients (17.6%) had SARS‐CoV‐2 infection, out of which 10 (27%) died during the acute phase of disease without evidence of thrombotic events. There was an increased risk of thrombotic events in COVID‐19 survivors compared to the non‐infected cohort (18.5% vs. 1.9%, p = 0.002) after a median follow‐up of 7 months. Multivariate regression analysis showed that COVID‐19 infection increased risk for late thrombotic events adjusted for age, sex, hypertension, diabetes, antithrombotic treatment, and previous thrombotic events (Odds Ratio (OR) 26.4, 95% confidence interval 2.5–280.6, p = 0.01). Clinical and laboratory markers did not predict thrombotic events. Conclusions There is an increased risk of late thrombotic complications in hemodialysis patients after infection with COVID‐19. Further studies should evaluate the benefit of prolonged prophylactic anticoagulation in hemodialysis patients after recovery from COVID‐19.

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IntroductionCOVID-19 is associated with an increased mortality in hemodialysis patients. Therefore, achieving a long-lasting effective immune response to SARS-CoV-2 vaccines is essential. This study describes the humoral immune response in hemodialysis patients following three doses of mRNA vaccines against SARS-CoV-2, and explores the factors associated with a sustained immune response.Materials and MethodsWe analyzed the monthly serological evolution of SARS-CoV-2 anti-S(RBD) antibodies for 1 year in 178 chronic hemodialysis patients who received three doses of SARS-CoV-2 mRNA vaccines. The primary outcome was sustained effective humoral response defined as anti-S(RBD) levels > 1,000 AU/ml after 4 months from the third dose. Multivariate logistic regression analyses were used to identify features associated with a sustained humoral immune response.ResultsAfter the initial two SARS-CoV-2 mRNA vaccine doses, 77.8% of patients showed an immediate effective humoral response, decreasing to 52.5% after 4 months. Antibody levels were significantly higher in COVID-exposed patients and HBV vaccine responders. After the third dose, 97% of patients showed an effective humoral response, and remained in 91.7% after 4 months. The mean monthly rate of antibody titer decline decreased from 33 ± 14.5 to 25 ± 16.7%. Multivariate regression analysis showed that previous exposure to COVID-19 and response to HBV vaccines were associated with an effective sustained humoral immune response.ConclusionImmunization with SARS-CoV-2 mRNA vaccines elicits an effective immediate humoral immune response in hemodialysis patients, with a progressive waning in antibody levels. A third booster dose enhances the immune response with significantly higher antibody levels and more sustained humoral immune response. COVID-naïve patients and patients without previous response to HBV vaccines are likely to benefit from receiving more booster doses to maintain an effective immune response.

Background and Aims There is an increased risk of thrombotic complications in patients with COVID-19. Hemodialysis patients are already at an increased risk for thromboembolic events such as stroke and pulmonary embolism. The aim of our study was to determine the incidence of late thrombotic complications (deep vein thrombosis, pulmonary embolism, stroke, new-onset vascular access thrombosis) in maintenance hemodialysis patients after recovery from COVID-19. Method We performed a retrospective cohort study of 200 prevalent hemodialysis patients in our center at the start of the pandemic. We excluded incident patients after the cohort entry date and those who required hemodialysis for acute kidney injury, and excluded patients with less than 1 month follow-up due to kidney transplantation or death from non-thrombotic causes. Results 185 prevalent hemodialysis patients finally met the inclusion criteria; 37 patients (17.6%) had SARS-CoV-2 infection, out of which 10 (27%) died during the acute phase of disease without evidence of thrombotic events. There was an increased risk of thrombotic events in COVID-19 survivors compared to the non-infected cohort (18.5% vs 1.9%, p=0.002) after a median follow-up of 7 months. Stroke incidence was 38.9 episodes/1000 patient-years in patients infected with SARS-CoV-2, compared to an incidence of 2.8 episodes/1000 patient-years in non-infected patients during the follow-up period. The median time from diagnosis of SARS-CoV-2 to the first thrombotic event was 62 days (interquartile range 5-118 days). Survival analysis with Kaplan-Meier curves revealed an increase in the rate of thrombotic events after SARS-CoV-2 compared to non-infected patients (see Figure 1). Mean survival from thrombotic event was 6.1±0.4 months in the COVID-infected group, compared to 6.97±0.04 months in the non-infected group (p<0.001). Multivariate regression analysis showed that COVID-19 infection increased risk for late thrombotic events adjusted for age, sex, hypertension, diabetes, antithrombotic treatment and previous thrombotic events (OR 26.4, 95% CI 2.5-280.6, p=0.01). Clinical and laboratory markers did not predict thrombotic events. Conclusion There is an increased risk of late thrombotic complications in hemodialysis patients after infection with COVID-19. Further studies should evaluate the benefit of prolonged prophylactic anticoagulation in hemodialysis patients after recovery from COVID-19.

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