COVID-19 variants of concern, particularly Delta, more harmful than original strain: Canadian study

A large study using Ontario case data suggests that COVID-19 variants of concern, particularly the Delta variant, cause more severe illness than the native strain of the virus, increasing the risk of hospitalization, admission to ICU and death.

The study found that people infected with VOCs were significantly younger and less likely to have comorbidities than those with non-VOC infections, and, even after adjusting for age, sex, comorbidities and other factors, the increased risk of adverse outcomes persisted.

Using case data from Ontario, the country’s most populated province, the study included 212,326 cases of COVID-19 reported between Feb. 7 and Jun. 26, 2021. Variants of concern included those with the N501Y mutation such as Alpha, Beta and Gamma as well as Delta, which have replaced the original SARS-CoV-2 strain.

Of the total cases, 22.4 per cent were non-VOC, 76.7 per cent were infections with N501Y mutations, and just 2.8 per cent were probable Delta.

The study found that with Alpha, Beta and Gamma VOC infections, risks of hospitalization were 52 per cent higher than non-VOC cases, with the risk of admission to ICU 89 per cent higher and death 51 per cent higher than the original virus.