Potential Risk Factors to COVID-19 Severity: Comparison of SARS-CoV-2 Delta- and Omicron-Dominant Periods

Continued study of risk factors can inform future pandemic preparedness and response. We aimed to determine the potential risk factors of COVID-19 severity among patients admitted to the hospital during the Delta- and Omicron-dominant periods.

We utilized the J-SPEED-style COVID-19 Hospital version, a pre-administered questionnaire, to collect data from hospitals in Hiroshima Prefecture between 8 August 2021 and 19 April 2022.

During the Delta-dominant period, patients aged over 65 (OR = 2.59, 95% CI = 1.75-3.84), males (OR = 1.42, 95% CI = 1.12-1.81) and with BMI exceeding 25 (OR = 1.99, 95% CI = 1.57-2.52), diabetes (OR = 2.03, 95% CI = 1.40-2.95), and those with fewer than two doses of vaccine (OR = 2.39, 95% CI = 1.46-3.91) were at a greater risk of severe COVID-19 compared to those without these risk factors. During the Omicron-dominant period, significantly greater severity was observed among patients over 65 years old (OR = 3.89, 95% CI = 2.95-5.12), males (OR = 1.76, 95% CI = 1.40-2.21), those with high blood pressure (OR = 1.30, 95% CI = 1.02-1.65), and mental disorder (OR = 2.22, 95% CI = 1.69-2.92) compared to patients without these risks.

Our findings indicate that risk factors vary across different SARS-CoV-2 variants. Examining variant-specific risk factors for COVID-19 severity can aid policymakers, public health specialists, and clinicians in prioritizing screening, treatment, and vaccination efforts, especially during potential healthcare resource shortages.