This study aims to assess the prognosis of inpatients with COVID-19 infection who have a history of sulfur mustard exposure.

We started a cohort study in October 2020 and ended in May 2021 on inpatients with COVID-19 infection who had been admitted to university healthcare centers. The analytic sample included 960 inpatients having COVID-19 infection (192 with; and 768 without sulfur mustard exposure). The exposed patients were male war veterans, and the unexposed patients were male individually age-matched people. All patients had a positive RT-PCR test and a positive chest CT for COVID-19. The outcome was death within 28 days of admission, and the predictors were clinical features recorded at patients' bedsides.

There was a significantly higher prevalence for asthma (p = 0.026) and pulmonary disease other than asthma (p < 0.001) in patients with the exposure. Sulfur mustard exposure was associated with increased risk for mortality of COVID-19 [hazard ratio (95% CI) = 1.92 (1.14,3.24), p = 0.013]. Early intubation signified a poor prognosis [hazard = 7.34 (4.65,11.58), p < 0.001]. However, individuals with higher PaO2 [hazard = 0.97 (0.95,0.98), p < 0.001], or people undergoing O2 therapy early upon admission [hazard = 0.58 (0.38,0.89), p = 0.011] showed lower risks for mortality. Individuals with asthma were at higher risk for mortality [hazard = 3.76 (1.69,8.36), p = 0.001].

Individuals with COVID-19 infection and sulfur mustard exposure should be considered high-risk patients and that, healthcare settings should be ready to provide critical care for them, including O₂ therapy. They are more likely to have asthma or other pulmonary diseases.