A recent research study states that large COVID-19 outbreaks in European nursing homes have skewed COVID-19 death data for older age groups.

This renders cross-country comparisons of the pandemic’s scale inaccurate.

Inconsistent data makes estimating the size and infection severity of the coronavirus pandemic a challenge. COVID-19 death rates are often used as an essential indicator of the pandemic size. However, researchers note that the COVID-19 death rates in the elderly population can hamper direct comparisons across countries of the underlying level of transmission. It is difficult to disentangle outbreaks in vulnerable populations from the general public. 

In countries such as Canada, the United Kingdom, and Sweden, over 20% of all reported COVID-19 deaths occur in nursing homes. In contrast, few COVID-19 deaths have been reported in nursing homes in South Korea and Singapore. Therefore, comparing the total number of fatalities across countries provides a misleading representation of the underlying level of transmission. 

Published in the leading journal Nature, scientists at the University of Cambridge and the Institut Pasteur analyzed age-specific COVID-19 death data from 45 countries and the results of 22 seroprevalence studies. The aim was to investigate the consistency of infection and fatality patterns across multiple countries. 

Results showed that the age distribution of deaths in those under 65 is remarkably consistent across different settings. They estimate that the infection-to-fatality ratio (IFR) is lowest among 5-9 years olds, with a linear increase by age among individuals older than 30 years. The data can be used to provide robust estimates of the share of the population that has been infected.

Among the 45 countries included in the study, scientists estimate that approximately 5% of these populations had been infected by the 1st of September 2020. Although, much higher transmission was thought to have occurred in several Latin American countries. Death rates from coronavirus in Peru equate to 0.01% of the country’s population. However, the model suggests that over half of Peru’s population has now been infected with COVID-19. This is a much higher infection rate than expected. 

The simple new modeling framework devised can help governments assess the pandemic’s progression and can be applied wherever reliable age-specific death data exists. It can also be used to predict the likelihood of dying from COVID-19 following infection, depending on a person’s age. 

Simply comparing the total number of deaths across countries can be misleading. Researchers highlight that studying coronavirus deaths among those under 65 is more reliable and gives a clearer insight into transmission rates. This enables better comparisons between countries, which is vital in building an ongoing pandemic response strategy. 

However, even after excluding data from the over 65’s, this new model shows that coronavirus death rates cannot be compared between some countries. This is because the relationship between infections and deaths is not consistent when other widespread ‘co-morbidity’ factors are involved.

This research study was funded by the University of Cambridge COVID-19 Rapid Response Grant. The scientists advise that this new model can be applied at a sub-national scale and may be useful in settings where extensive seroprevalence studies might not be feasible.

Written by Helen Massy, BSc.

References:

O’Driscoll, M., Dos Santos, G., Wang, L., Cummings, D., Azman, A., Paireau, J., Fontanet, A., Cauchemez, S. and Salje, H., 2020. Age-specific mortality and immunity patterns of SARS-CoV-2. Nature,.

Image by Miroslava Chrienova from Pixabay