HLA haplotypes were found to be associated with increased risk for viral infections or disease severity in various diseases, including SARS. Several genetic variants are associated with COVID-19 severity. Studies have proposed associations, based on a very small sample and a large number of tested HLA alleles, but no clear association between HLA and COVID-19 incidence or severity has been reported. We conducted a large-scale HLA analysis of Israeli individuals who tested positive for SARS-CoV-2 infection by PCR. Overall, 72,912 individuals with known HLA haplotypes were included in the study, of whom 6413 (8.8%) were found to have SARS-CoV-2 by PCR. A total of 20,937 subjects were of Ashkenazi origin (at least 2/4 grandparents). One hundred eighty-one patients (2.8% of the infected) were hospitalized due to the disease. None of the 66 most common HLA loci (within the five HLA subgroups: A, B, C, DQB1, DRB1) was found to be associated with SARS-CoV-2 infection or hospitalization in the general Israeli population. Similarly, no association was detected in the Ashkenazi Jewish subset. Moreover, no association was found between heterozygosity in any of the HLA loci and either infection or hospitalization. We conclude that HLA haplotypes are not a major risk/protecting factor among the Israeli population for SARS-CoV-2 infection or severity. Our results suggest that if any HLA association exists with the disease it is very weak, and of limited effect on the pandemic.

BACKGROUND: Emerging data suggest increased arterial thrombosis risk in the months preceding a cancer diagnosis.

OBJECTIVES: To assess whether patients without documented vascular risk factors or pre-existing cardiovascular disease have a higher relative risk of cancer 12 months after arterial thrombotic events (ATE), compared to unselected patients.

PATIENTS/METHODS: A population-based cohort study of Clalit Health Services (CHS) database included CHS members ≥25 years without prior cancer or ATE (n = 2 804 584). An iterative matching process selected 10 potential controls chronologically for each consecutive exposed, age- and sex-matched (actual controls drawn 1:1 from a lot). Study exposure, ATE, was defined as ischemic stroke, transient ischemic attack, myocardial infarction or systemic arterial thromboembolism during hospitalization. The outcome was newly-diagnosed cancer within 12 months, based on Israeli national cancer registry. Cox proportional hazards multivariate regression calculated hazard ratio (HR) for outcomes, adjusted for cancer risk factors. Analysis also performed for three subgroups: age ≤50 years; no cardiovascular risk factors; no prior cardiovascular disease.

RESULTS: The full ATE and matched control cohorts included 43 108 patients. The 12-month cumulative incidence of cancer (95% confidence interval) was 0.020 (0.019-0.022) in the ATE cohort and 0.012 (0.011-0.013) in controls, corresponding to an adjusted HR of 1.665 (1.489-1.862). The relative risk of cancer was high in all subgroups up to a HR of 3.754 (1.912-7.372) in patients without cardiovascular risk factors.

CONCLUSION: There is an increased risk of previously undiagnosed cancer at 12 months after ATE, especially in patients without documented vascular risk factors or pre-existent cardiovascular disease.

Evidence regarding the effectiveness of covid-19 vaccine in patients with impaired immunity, is limited. Initial observations suggest a lower humoral response in these patients. We evaluated the relative effectiveness of the mRNA BNT162b2 vaccine in patients with hematological neoplasms compared to matched controls. Data on patients with hematological neoplasms after two vaccine doses were extracted and matched 1:1 with vaccinated controls. Subpopulation analyses focused on patients receiving therapy for the hematological neoplasm, patients without treatment who are only followed, and recipients of specific treatments. The analysis focused on covid-19 outcomes from day 7 through 43 following the second vaccine dose: Documented covid-19 infection by PCR; Symptomatic infection; Hospitalizations; Severe covid-19 disease and covid-19-related death. Of a population of 4.7 million insured people, 32,516 patients with hematological neoplasms were identified, of whom 5,017 were receiving therapy for an active disease. Vaccinated patients with hematological neoplasms, compared with vaccinated matched controls, had an increased risk of documented infections (RR 1.60, 95% confidence interval [CI] 1.12-2.37), symptomatic covid-19 (RR 1.72, 95% CI 1.05-2.85), covid-19 related hospitalizations (RR 3.13, 95% CI 1.68-7.08), severe covid-19 (RR 2.27, 95% CI 1.18-5.19) and covid-19 related death (RR 1.66, 95% CI 0.72-4.47). Limiting the analysis to patients on hematological treatments showed a higher increased risk. This analysis shows that vaccinated patients with hematological neoplasms, in particular patients on treatment, suffer from covid-19 outcomes more than vaccinated individuals with intact immune system. Ways to enhance covid-19 immunity in this patient population, such as additional doses, should be explored.

To evaluate the effectiveness of the BNT162b2 messenger RNA vaccine in pregnant women, we conducted an observational cohort study of pregnant women aged 16 years or older, with no history of SARS-CoV-2, who were vaccinated between 20 December 2020 and 3 June 2021. A total of 10,861 vaccinated pregnant women were matched to 10,861 unvaccinated pregnant controls using demographic and clinical characteristics. Study outcomes included documented infection with SARS-CoV-2, symptomatic COVID-19, COVID-19-related hospitalization, severe illness and death. Estimated vaccine effectiveness from 7 through to 56 d after the second dose was 96% (95% confidence interval 89-100%) for any documented infection, 97% (91-100%) for infections with documented symptoms and 89% (43-100%) for COVID-19-related hospitalization. Only one event of severe illness was observed in the unvaccinated group and no deaths were observed in either group. In summary, the BNT162b2 mRNA vaccine was estimated to have high vaccine effectiveness in pregnant women, which is similar to the effectiveness estimated in the general population.

OBJECTIVE: To illustrate the problem of subpopulation miscalibration, to adapt an algorithm for recalibration of the predictions, and to validate its performance.

MATERIALS AND METHODS: In this retrospective cohort study, we evaluated the calibration of predictions based on the Pooled Cohort Equations (PCE) and the fracture risk assessment tool (FRAX) in the overall population and in subpopulations defined by the intersection of age, sex, ethnicity, socioeconomic status, and immigration history. We next applied the recalibration algorithm and assessed the change in calibration metrics, including calibration-in-the-large.

RESULTS: 1 021 041 patients were included in the PCE population, and 1 116 324 patients were included in the FRAX population. Baseline overall model calibration of the 2 tested models was good, but calibration in a substantial portion of the subpopulations was poor. After applying the algorithm, subpopulation calibration statistics were greatly improved, with the variance of the calibration-in-the-large values across all subpopulations reduced by 98.8% and 94.3% in the PCE and FRAX models, respectively.

DISCUSSION: Prediction models in medicine are increasingly common. Calibration, the agreement between predicted and observed risks, is commonly poor for subpopulations that were underrepresented in the development set of the models, resulting in bias and reduced performance for these subpopulations. In this work, we empirically evaluated an adapted version of the fairness algorithm designed by Hebert-Johnson et al. (2017) and demonstrated its use in improving subpopulation miscalibration.

CONCLUSION: A postprocessing and model-independent fairness algorithm for recalibration of predictive models greatly decreases the bias of subpopulation miscalibration and thus increases fairness and equality.

BACKGROUND: Many countries are experiencing a resurgence of COVID-19, driven predominantly by the delta (B.1.617.2) variant of SARS-CoV-2. In response, these countries are considering the administration of a third dose of mRNA COVID-19 vaccine as a booster dose to address potential waning immunity over time and reduced effectiveness against the delta variant. We aimed to use the data repositories of Israel's largest health-care organisation to evaluate the effectiveness of a third dose of the BNT162b2 mRNA vaccine for preventing severe COVID-19 outcomes.

METHODS: Using data from Clalit Health Services, which provides mandatory health-care coverage for over half of the Israeli population, individuals receiving a third vaccine dose between July 30, 2020, and Sept 23, 2021, were matched (1:1) to demographically and clinically similar controls who did not receive a third dose. Eligible participants had received the second vaccine dose at least 5 months before the recruitment date, had no previous documented SARS-CoV-2 infection, and had no contact with the health-care system in the 3 days before recruitment. Individuals who are health-care workers, live in long-term care facilities, or are medically confined to their homes were excluded. Primary outcomes were COVID-19-related admission to hospital, severe disease, and COVID-19-related death. The third dose effectiveness for each outcome was estimated as 1 - risk ratio using the Kaplan-Meier estimator.

FINDINGS: 1 158 269 individuals were eligible to be included in the third dose group. Following matching, the third dose and control groups each included 728 321 individuals. Participants had a median age of 52 years (IQR 37-68) and 51% were female. The median follow-up time was 13 days (IQR 6-21) in both groups. Vaccine effectiveness evaluated at least 7 days after receipt of the third dose, compared with receiving only two doses at least 5 months ago, was estimated to be 93% (231 events for two doses vs 29 events for three doses; 95% CI 88-97) for admission to hospital, 92% (157 vs 17 events; 82-97) for severe disease, and 81% (44 vs seven events; 59-97) for COVID-19-related death.

INTERPRETATION: Our findings suggest that a third dose of the BNT162b2 mRNA vaccine is effective in protecting individuals against severe COVID-19-related outcomes, compared with receiving only two doses at least 5 months ago.

FUNDING: The Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute.