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The effectiveness of a third mRNA COVID-19 vaccine dose (booster dose) against the Omicron (B.1.1.529) variant is uncertain, especially in older, high-risk populations.To determine mRNA booster vaccine effectiveness (VE) against SARS-CoV-2 infection, hospitalization, and death in the Omicron era by booster type, primary vaccine type, time since primary vaccination, age, and comorbidity burden.Retrospective matched cohort study designed to emulate a target trial of booster vaccination versus no booster, conducted from 1 December 2021 to 31 March 2022.U.S. Department of Veterans Affairs health care system.Persons who had received 2 mRNA COVID-19 vaccine doses at least 5 months earlier.Booster monovalent mRNA vaccination (Pfizer-BioNTech's BNT162b2 or Moderna's mRNA-1273) versus no booster.Booster VE.Each group included 490 838 well-matched persons, who were predominantly male (88%), had a mean age of 63.0 years (SD, 14.0), and were followed for up to 121 days (mean, 79.8 days). Booster VE more than 10 days after a booster dose was 42.3% (95% CI, 40.6% to 43.9%) against SARS-CoV-2 infection, 53.3% (CI, 48.1% to 58.0%) against SARS-CoV-2-related hospitalization, and 79.1% (CI, 71.2% to 84.9%) against SARS-CoV-2-related death. Booster VE was similar for different booster types (BNT162b2 or mRNA-1273), age groups, and primary vaccination regimens but was significantly higher with longer time since primary vaccination and higher comorbidity burden.Predominantly male population.Booster mRNA vaccination was highly effective in preventing death and moderately effective in preventing infection and hospitalization for up to 4 months after administration in the Omicron era. Increased uptake of booster vaccination, which is currently suboptimal, should be pursued to limit the morbidity and mortality of SARS-CoV-2 infection, especially in persons with high comorbidity burden.U.S. Department of Veterans Affairs.

In a target trial emulation study that included nearly 6 million predominately male patients receiving care in the U.S. Department of Veterans Affairs health care system, those receiving messenger RNA vaccines against SARS-CoV-2 were matched 1:1 to unvaccinated controls according to demographic, clinical, and geographic characteristics and followed for SARS-CoV-2 infection or SARS-CoV-2–related death to determine vaccine efficacy., Visual Abstract. COVID-19 Vaccination Effectiveness Against Infection or Death. In a target trial emulation study that included nearly 6 million predominately male patients receiving care in the U.S. Department of Veterans Affairs health care system, those receiving messenger RNA vaccines against SARS-CoV-2 were matched 1:1 to unvaccinated controls according to demographic, clinical, and geographic characteristics and followed for SARS-CoV-2 infection or SARS-CoV-2–related death to determine vaccine efficacy. Visual Abstract. COVID-19 Vaccination Effectiveness Against Infection or Death. In a target trial emulation study that included nearly 6 million predominately male patients receiving care in the U.S. Department of Veterans Affairs health care system, those receiving messenger RNA vaccines against SARS-CoV-2 were matched 1:1 to unvaccinated controls according to demographic, clinical, and geographic characteristics and followed for SARS-CoV-2 infection or SARS-CoV-2–related death to determine vaccine efficacy., Background: Little is known about real-world COVID-19 vaccine effectiveness (VE) in racially and ethnically diverse, elderly populations with high comorbidity burden. Objective: To determine the effectiveness of messenger RNA COVID-19 vaccines. Design: Target trial emulation study comparing newly vaccinated persons with matched unvaccinated controls. Setting: U.S. Department of Veterans Affairs health care system. Participants: Among persons receiving care in the Veterans Affairs health care system (n = 5 766 638), those who received at least 1 dose of the Moderna or Pfizer–BioNTech COVID-19 vaccine from 11 December 2020 to 25 March 2021 (n = 2 099 871) were matched to unvaccinated controls in a 1:1 ratio according to demographic, clinical, and geographic characteristics. Intervention: Follow-up for SARS-CoV-2 infection or SARS-CoV-2–related death, defined as death within 30 days of infection, began after the vaccination date or an identical index date for the matched unvaccinated controls and continued until up to 30 June 2021. Measurements: Vaccine effectiveness against SARS-CoV-2 infection or SARS-CoV-2–related death. Results: Vaccinated and unvaccinated groups were well matched; both were predominantly male (92.9% vs. 93.4%), had advanced age (mean, 68.7 years in both groups), had diverse racial and ethnic distribution (for example, Black: 17.3% vs. 17.0%, Hispanic: 6.5% vs. 6.1%), and had substantial comorbidity burden. Vaccine effectiveness 7 or more days after the second vaccine dose was 69% (95% CI, 67% to 70%) against SARS-CoV-2 infection and 86% (CI, 82% to 89%) against SARS-CoV-2–related death and was similar when follow-up was extended to 31 March versus 30 June. Vaccine effectiveness against infection decreased with increasing age and comorbidity burden. Limitation: Predominantly male population and lack of data on SARS-CoV-2 variants. Conclusion: In an elderly, diverse, high-comorbidity population, COVID-19 VE against infection was substantially lower than previously reported, but VE against death was high. Complementary infection mitigation efforts remain important for pandemic control, even with vaccination. Primary Funding Source: U.S. Department of Veterans Affairs.

DNA-based HFE gene testing can confirm hereditary hemochromatosis in most people of Northern European descent. However, liver biopsy is important to detect cirrhosis.To develop noninvasive criteria to predict the presence or absence of advanced hepatic fibrosis or cirrhosis in Americans with hemochromatosis.Cross-sectional study.Six tertiary care referral clinics.182 patients with phenotypically defined hemochromatosis.Liver histopathology and serum ferritin, aspartate aminotransferase, and alanine aminotransferase levels. Multivariate logistic regression analysis was used to examine factors associated with cirrhosis (defined as bridging fibrosis or unequivocal cirrhosis on biopsy).Cirrhosis was present in 40 of 182 (22%) patients in the overall group and in 35 of 147 (24%) of C282Y homozygotes. Only 1 of 93 patients with a serum ferritin level less than 1000 microg/L had cirrhosis compared with 39 of 89 patients with serum ferritin levels greater than 1000 microg/L (P0.001). No C282Y homozygotes or C282Y/H63D compound heterozygotes with serum ferritin levels less than 1000 microg/L had cirrhosis. Elevated serum aminotransferase levels (P = 0.001) and serum ferritin levels greater than 1000 microg/L (P = 0.001), but not age older than 40 years (P = 0.2), were independently associated with cirrhosis. In a multivariate model, the probability of cirrhosis was 7.4% among patients with serum ferritin levels less than 1000 microg/L compared with 72% among patients with serum ferritin levels greater than 1000 microg/L after adjustment for age and elevated serum liver enzyme levels.Patients with hemochromatosis and serum ferritin levels less than 1000 microg/L are unlikely to have cirrhosis. Liver biopsy to screen for cirrhosis may be unnecessary in such patients, regardless of age or serum liver enzyme levels.