Lessons from COVID-19 mortality data across countries

Several online sources provide up-to-date open-access data on numbers, rates and proportions of COVID-19 deaths. Our article aims of comparing and interpreting between-country trends of mortality rate, case-fatality and all-cause excess mortality.

We used data from open databases (Our World in Data mostly) for comparing mortality of eleven western countries (Austria, Belgium, Canada, France, Germany, Italy, Netherlands, Spain, Sweden, UK, USA). Between-country trends in mortality rate and case-fatality (both including deaths for COVID-19 as numerator and therefore labelled as COVID-19 mortality metrics) and all-cause excess mortality (i.e. observed deaths during the epidemic compared with those expected based on mortality in the same periods of previous years) were compared.

Although Belgium ranks first in mortality from COVID-19 (possibly due to the broadest criterion for attributing a death to COVID-19), it does not rank first for all-cause excess mortality. Conversely, compared with Belgium, the UK, Italy and Spain have reported lower COVID-19 mortality (possibly due to the narrower definitions for a COVID-19 death) but higher all-cause excess mortality. Germany and Austria are the unique countries for which COVID-19 mortality, case-fatality and all-cause excess mortality consistently exhibited the lowest rates.

Between-country heterogeneity of COVID-19 mortality metrics could be largely explained by differences of criteria for attributing a death to COVID-19; in age/comorbidity structures; in policies for identifying asymptomatic people affected from SARS-CoV-2 infection. All-cause excess mortality is recommended as a more reliable metric for comparing countries.