Clinical and social determinants of COVID-19 lethality and ICU admission across variant waves in the Brazilian Amazon.

BACKGROUND: The state of Amazonas, located in the Brazilian Amazon, was disproportionately affected during the first waves of the COVID-19 pandemic. METHODS: We conducted a population-based cohort study including all confirmed COVID-19 cases (2020-2) in the state of Amazonas, located in northern Brazil, linking data from three surveillance systems with cases of influenza-like illness (ILI) and severe acute respiratory syndrome (SARS). Outcomes included death, intensive care unit (ICU) admission, and a composite severity outcome. RESULTS: Among 420 819 cases, 378 142 (89.9%) had ILI and 42 677 (10.1%) had SARS. A substantial burden of severe outcomes was observed among SARS cases, with ∼25% (n = 8910/35 909) of patients admitted to the ICU, 21.1% (n = 7229/34 323) requiring invasive mechanical ventilation, and 36.7% (n = 14 971/40 837) dying. Male sex [odds ratio (OR) = 1.23; 95% confidence interval (CI): 1.15-1.31; P < .001], age of ≥70 years (OR = 13.73; 95% CI: 11.97-15.76; P < .001), Indigenous ethnicity (OR = 2.32; 95% CI: 1.85-2.91; P < .001), dyspnea (OR = 1.99; 95% CI: 1.82-2.19; P < .001), loss of smell (OR = 1.54; 95% CI: 1.31-1.81; P < .001), and comorbidities, including chronic kidney disease (OR = 1.94; 95% CI: 1.58-2.39; P < .001), chronic respiratory disease (OR = 1.38; 95% CI: 1.08-1.77; P < .05), diabetes (OR = 1.12; 95% CI: 1.03-1.22; P < .05), obesity (OR = 1.31; 95% CI: 1.13-1.51; P < .001), and immunosuppression (OR = 1.90; 95% CI: 1.48-2.44; P < .001), were independently associated with a higher risk of death. Lethality increased significantly during the Gamma wave (OR = 3.76; 95% CI: 3.34-4.24; P < .001). CONCLUSION: The severity of COVID-19 in Amazonas was shaped by biological, structural, and viral factors, highlighting the need for equitable strengthening of the health system.