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- Title
Estimates of SARS-CoV-2 Omicron BA.2 Subvariant Severity in New England.
- Authors
Strasser, Zachary H.; Greifer, Noah; Hadavand, Aboozar; Murphy, Shawn N.; Estiri, Hossein
- Abstract
This cohort study evaluates the odds of mortality in patients infected with the SARS-CoV-2 Omicron BA.2 subvariant compared with the Delta (B.1.617.2) and Omicron (B.1.1.529) variants in New England. Key Points: Question: Is the SARS-CoV-2 Omicron BA.2 subvariant lineage intrinsically less severe than previous variants after taking into account demographics, comorbidities, prior infections, vaccinations, and treatments? Findings: In this cohort study of 101 470 patients, mortality rates were 0.7% for Delta (B.1.617.2), 0.4% for Omicron (B.1.1.529), and 0.3% for Omicron (BA.2) subvariants. After adjusting for confounding factors, the risk of death was significantly lower with the Omicron subvariant BA.2 compared with those of the Omicron and Delta variants. Meaning: Observational data that adjusts for confounders suggest that the Omicron BA.2 variant is intrinsically less severe than previous variants. Importance: The SARS-CoV-2 Omicron subvariant, BA.2, may be less severe than previous variants; however, confounding factors make interpreting the intrinsic severity challenging. Objective: To compare the adjusted risks of mortality, hospitalization, intensive care unit admission, and invasive ventilation between the BA.2 subvariant and the Omicron and Delta variants, after accounting for multiple confounders. Design, Setting, and Participants: This was a retrospective cohort study that applied an entropy balancing approach. Patients in a multicenter inpatient and outpatient system in New England with COVID-19 between March 3, 2020, and June 20, 2022, were identified. Exposures: Cases were assigned as being exposed to the Delta (B.1.617.2) variant, the Omicron (B.1.1.529) variant, or the Omicron BA.2 lineage subvariants. Main Outcomes and Measures: The primary study outcome planned before analysis was risk of 30-day mortality. Secondary outcomes included the risks of hospitalization, invasive ventilation, and intensive care unit admissions. Results: Of 102 315 confirmed COVID-19 cases (mean [SD] age, 44.2 [21.6] years; 63 482 women [62.0%]), 20 770 were labeled as Delta variants, 52 605 were labeled as the Omicron B.1.1.529 variant, and 28 940 were labeled as Omicron BA.2 subvariants. Patient cases were excluded if they occurred outside the prespecified temporal windows associated with the variants or had minimal longitudinal data in the Mass General Brigham system before COVID-19. Mortality rates were 0.7% for Delta (B.1.617.2), 0.4% for Omicron (B.1.1.529), and 0.3% for Omicron (BA.2). The adjusted odds ratio of mortality from the Delta variant compared with the Omicron BA.2 subvariants was 2.07 (95% CI, 1.04-4.10) and that of the original Omicron variant compared with the Omicron BA.2 subvariant was 2.20 (95% CI, 1.56-3.11). For all outcomes, the Omicron BA.2 subvariants were significantly less severe than that of the Omicron and Delta variants. Conclusions and Relevance: In this cohort study, after having accounted for a variety of confounding factors associated with SARS-CoV-2 outcomes, the Omicron BA.2 subvariant was found to be intrinsically less severe than both the Delta and Omicron variants. With respect to these variants, the severity profile of SARS-CoV-2 appears to be diminishing after taking into account various factors including therapeutics, vaccinations, and prior infections.
- Subjects
NEW England; INTENSIVE care units; RESEARCH; COVID-19; CONFIDENCE intervals; RETROSPECTIVE studies; ACQUISITION of data; SEVERITY of illness index; ARTIFICIAL respiration; RISK assessment; COMPARATIVE studies; HOSPITAL care; MEDICAL records; DESCRIPTIVE statistics; RESEARCH funding; ODDS ratio; LONGITUDINAL method
- Publication
JAMA Network Open, 2022, Vol 5, Issue 10, pe2238354
- ISSN
2574-3805
- Publication type
Article
- DOI
10.1001/jamanetworkopen.2022.38354