Research Briefs

Refined mortality rates of COVID-19 using data from 45 countries

Nov. 20, 2020: A new study refines COVID-19 mortality rates across countries according to age and extrapolates infection rates to estimate the pandemic's size.

Refined mortality rates of COVID-19 using data from 45 countries

Colorized transmission electron micrograph of SARS-CoV-2 virions emerging from a cell, image by CDC/NIAID.

Countries report deaths from COVID-19 in different ways, which has created challenges for researchers who seek to uncover the pandemic’s global mortality patterns. While it’s long been known that elderly people are more at risk of death from this disease, exact estimates by age have varied.

A new study published Nov. 2 in Nature sought to refine our knowledge of age-associated mortality risks from COVID-19, and UF preeminence professor Derek Cummings contributed to the work. The study also analyzed the seroprevalence of antibodies indicating infection-derived immunity to COVID-19 to validate their model’s estimate of infection rates based on reported deaths.

Cummings is a professor in the College of Liberal Arts and Sciences Department of Biology, and an EPI faculty member, who specializes in modeling transmission dynamics, immunity patterns, and aspects of both classic and emerging diseases. By studying reliably reported death rates, he and his collaborators were able to estimate the number of people infected with COVID-19 in various countries. They then used seroprevalence studies, which detect infection-derived immunity, to validate the accuracy of their model.

The researchers found that age-specific mortality from COVID-19 ranged from 0.001% in five to nine-year-old children, to 8.29% for those aged 80 and older. They also estimated that every five-year increase in age yields a mean absolute increase in mortality of 0.59%. But sex factors heavily: in the 80-plus age group, men experience a mortality rate of 10.83% while for women it is only 5.76%. Last, the study estimates that roughly 5% of each country’s populace was infected by Sept. 1, with higher transmission rates likely in some Latin American countries. This means that the vast majority of people are still susceptible to contracting the infection.

The study also shows that mortality rates vary by country, which hints at behavioral influences that may drive COVID-19 infection-to-fatality ratios.

Mortality rates by country of COVID-19

Figure 1 from the paper shows the infection-to-fatality ratio by country. Left, lower observed mortality; right, higher observed mortality. Color-coded by continent.

COVID-19 attack rates per country.

Figure 2 from the paper shows graphs that estimate the proportion of named countries' populations that have been infected with COVID-19 over time. 

Read more

O'Driscoll M, Ribeiro Dos Santos G, Wang L, et al. Age-specific mortality and immunity patterns of SARS-CoV-2. Nature. 2021;590(7844):140-145. doi:10.1038/s41586-020-2918-0

Written by DeLene Beeland