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Age-specific mortality and immunity patterns of SARS-CoV-2

Abstract

Estimating the size of the coronavirus disease (COVID-19) pandemic and the infection severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is made challenging by inconsistencies in the available data. The number of deaths associated with COVID-19 is often used as a key indicator for the size of the epidemic, but the observed number of deaths represents only a minority of all infections1,2. In addition, the heterogeneous burdens in nursing homes and the variable reporting of deaths of older individuals can hinder direct comparisons of mortality rates and the underlying levels of transmission across countries3. Here we use age-specific COVID-19-associated death data from 45 countries and the results of 22 seroprevalence studies to investigate the consistency of infection and fatality patterns across multiple countries. We find that the age distribution of deaths in younger age groups (less than 65 years of age) is very consistent across different settings and demonstrate how these data can provide robust estimates of the share of the population that has been infected. We estimate that the infection fatality ratio is lowest among 5–9-year-old children, with a log-linear increase by age among individuals older than 30 years. Population age structures and heterogeneous burdens in nursing homes explain some but not all of the heterogeneity between countries in infection fatality ratios. Among the 45 countries included in our analysis, we estimate that approximately 5% of these populations had been infected by 1 September 2020, and that much higher transmission rates have probably occurred in a number of Latin American countries. This simple modelling framework can help countries to assess the progression of the pandemic and can be applied in any scenario for which reliable age-specific death data are available.

Data availability

Data are available at https://github.com/meganodris/International-COVID-IFR.

Code availability

All code necessary to reproduce this analysis is available at https://github.com/meganodris/International-COVID-IFR.

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Acknowledgements

We acknowledge financial support from the EPSRC Impact Acceleration Grant (number RG90413) (M.O., H.S., G.R.D.S. and L.W.), the European Research Council (grant 804744) (H.S.), the Investissement d’Avenir program (S.C.), the Laboratoire d’Excellence Integrative Biology of Emerging Infectious Diseases program (grant ANR-10-LABX-62- IBEID) (S.C.), Santé Publique France (S.C.), the INCEPTION project (PIA/ANR16-CONV-0005) (S.C.) and the European Union’s Horizon 2020 research and innovation program under grants 101003589 (RECOVER) and 874735 (VEO) (S.C.). We thank the global public health community for the rapid synthesis of SARS-CoV-2-related data.

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M.O., H.S. and S.C. conceived the study and performed the analysis. M.O., H.S., S.C., G.R.D.S., L.W. and J.P. collated data. G.R.D.S. and L.W. reviewed code. M.O., H.S. and S.C. wrote the first draft of the manuscript. M.O., H.S., S.C., G.R.D.S., L.W., D.A.T.C., A.S.A., J.P. and A.F. discussed the results and contributed to revisions of the manuscript.

Corresponding authors

Correspondence to Megan O’Driscoll or Simon Cauchemez or Henrik Salje.

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The authors declare no competing interests.

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Peer review information Nature thanks Gabriel Leung, Geert Molenberghs and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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This file contains Supplementary Methods, Supplementary Tables 1-4, Supplementary Figures 1-12 and Supplementary References.

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O’Driscoll, M., Dos Santos, G.R., Wang, L. et al. Age-specific mortality and immunity patterns of SARS-CoV-2. Nature (2020). https://doi.org/10.1038/s41586-020-2918-0

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