Age-Dependence of Hospitalization and Fatality for Different SARS-CoV-2 Variants of Concern in Ontario, Canada

Abstract

Age plays a crucial role in the severity of COVID-19 infections. This study aims to compare the severe effects of the dominant variants of concern in Ontario, Canada, and examine how the relationship between age and serious outcomes evolved throughout the pandemic. We analyzed 1,526,024 incidence records of SARS-CoV-2, collected by Public Health Ontario from January 23, 2020, to December 6, 2022, to construct age distributions for known infections (KIs), hospitalizations, and fatalities. By examining hospitalization and fatality probabilities across different age groups during the periods when the Ancestral, Alpha, Delta, and Omicron variants were dominant, we found that older age groups consistently faced higher risks. The Alpha and Delta periods exhibited the highest probabilities of hospitalization and fatality among older individuals, while the Omicron epoch showed the lowest. The roll-out of vaccines and the implementation of varying restrictions during different waves of the pandemic likely influenced these outcomes, highlighting the relationship between age, variant transmissibility, and public health measures.