Relative risks of Covid-19 fatality between the first and second waves of the pandemic in Ontario, Canada

Hsu, Sylvia H.; Chang, Su-Hsin; Gross, Cary; Wang, Shi-Yi

OBJECTIVES: To examine whether the case fatality rate (CFR) of coronavirus disease 2019 (Covid-19) decreased overtime, and whether the Covid-19 testing rate is a driving factor for the changes if the CFR decreased. METHODS: Analyzing Covid-19 cases, deaths, and tests in Ontario, Canada, we compared the CFR between the first wave and the second wave across 26 Public Health Units in Ontario. We also explored whether a high testing rate was associated with a large CFR decrease. RESULTS: The first wave CFR ranged from 0.004 to 0.146; whereas the second wave CFR ranged from 0.003 to 0.034. The pooled RR estimate of the second wave Covid-19 case fatality, compared to first wave, was 0.24 (95% CI: 0.19-0.32). Additionally, Covid-19 testing percentages were not associated with the estimated RR (p-value = 0.246). CONCLUSIONS: The Covid-19 CFR decreased profoundly in Ontario during the second wave, and Covid-19 testing was not a driving factor for this decrease.