How age and underlying conditions affect incidence of hospitalization and death after documented COVID-19 diagnosis among individuals aged >=20 years, a retrospective cohort study using PCORnet, April 2022 to March 2025

The study examined how age and underlying medical conditions affect the risk of hospitalization and death after COVID-19 in 1,662,679 patients between April 2022 and March 2025. The incidence of hospitalization increased with age: 4.7% in individuals aged 20–49 years, 6.3% in those aged 50–64 years, 10.8% in those aged 65–79 years, and 22.6% in those over 80 years old. Similarly, mortality rates increased: 0.11%, 0.42%, 1.0%, and 3.6% in the respective age groups. Within each age group, the incidence of hospitalization and death increased with the number of underlying conditions, with the highest incidence among patients with three or more conditions. Results showed that individuals with two or more underlying medical conditions had higher incidence of both complications across all age groups. Advanced age remained strongly associated with hospitalization and mortality after COVID-19.