Age-specific mortality and immunity patterns of SARS-CoV-2 infection in 45 countries (preprint)

ABSTRACT

The number of COVID-19 deaths is often used as a key indicator of SARS-CoV-2 epidemic size. However, heterogeneous burdens in nursing homes and variable reporting of deaths in elderly individuals can hamper comparisons of deaths and the number of infections associated with them across countries. Using age-specific death data from 45 countries, we find that relative differences in the number of deaths by age amongst individuals aged <65 years old are highly consistent across locations. Combining these data with data from 15 seroprevalence surveys we demonstrate how age-specific infection fatality ratios (IFRs) can be used to reconstruct infected population proportions. We find notable heterogeneity in overall IFR estimates as suggested by individual serological studies and observe that for most European countries the reported number of deaths amongst [≥]65s are significantly greater than expected, consistent with high infection attack rates experienced by nursing home populations in Europe. Age-specific COVID-19 death data in younger individuals can provide a robust indicator of population immunity.