A recent publication in the peer-reviewed Canadian Medical Association Journal documents the enhanced virulence of the Delta strain of SARS-CoV-2 virus. The study was based on 212,326 cases of infection with a non-variant of concern virus and approximately 800,000 patients with a variant virus of concern including Alpha, Beta, Gamma and Delta strains. The Delta variant emerged in Canada in April at the midpoint of the study that extended from the first week of February to the last week of June 2021.
Patients infected with a variant of concern demonstrated a 52 percent increased risk of hospitalization, an 89 percent increased risk of admission to an intensive care unit and a 51 percent increased risk of death. The Delta variant doubled the risk of infection and resulted in a 235 percent increased risk of ICU admission and a 133 percent increased risk of death. Patients infected with a variant of concern including Delta were younger and were without co-morbidities compared to earlier admissions infected by the original SARS-CoV-2 virus.
The study determined that vaccination sharply reduced hospitalization and death, although vaccinated patients were susceptible to infection.