Estimates of the excess mortality associated with the COVID-19 pandemic from the World Health Organization

Abstract As a part of its mandate to compile and disseminate statistics on mortality, the World Health Organization (WHO) has been tracking the progression of the COVID-19 pandemic since the beginning of 2020. However, reported statistics on COVID-19 are problematic for a number of countries due to variations in testing access, differential diagnostic capacity and inconsistencies in the applications of standards to correctly certify COVID-19 as cause-of-death. In addition, the pandemic has caused extensive collateral damage beyond what is directly attributable to it. Consequently, the WHO has estimated excess deaths for each country for the years 2020 and 2021 to quantify the pandemic’s impact more comprehensively and consistently. Defined as the number of deaths in a particular period, relative to that expected during “normal times”, excess deaths capture both the direct and indirect impacts of a crisis. The data required to estimate the excess mortality associated with the COVID-19 pandemic i.e., time-series of known deaths during the pandemic period and historical time-series of the same to forecast into the pandemic period as “expected”, are only available for a subset of countries. This paper describes the methods used to estimate the global, regional, and country specific estimates of excess mortality for the years 2020 and 2021 and provides an overview of the resultant estimates. The full details of the method development, validation and performance are provided in a separate report. In summary, excess deaths have been derived by the WHO using an over-dispersed Poisson count framework that applies Bayesian inference techniques to quantify uncertainty. The framework utilizes data from locations that have recorded national monthly data to build a loglinear regression model with both time-varying and time-invariant coefficients. The model is used to predict excess deaths in locations without any all-cause mortality data reported during the pandemic period. Furthermore, certain countries have only subnational data for the period. For these, the framework is used to build country-specific multinomial models that use pre-pandemic subnational data and subnational data reported during the pandemic to predict national level monthly mortality for years 2020 and 2021. Globally, 14.91 million excess deaths are estimated with a 95% Uncertainty Interval (UI) from 13.32 million to 16.64 million which is 2.75 (UI 2.45 to 3.07) times higher than the 5.42 million COVID-19 deaths reported for the period. There is wide variation in the excess estimates across the six WHO regions. African Region accounts for 1.25 million excess deaths (UI 0.91 million to 1.58 million), Region of the Americas for 3.23 million excess deaths (UI 3.16 million to 3.30 million), Eastern Mediterranean Region for 1.08 million excess deaths (UI 0.87 million to 1.30 million), European Region for 3.25 million excess deaths (UI 3.18 million to 3.32 million), South-East Asia Region for 5.99 million excess deaths (4.50 million to 7.72 million) and Western Pacific Region accounting for 120 thousand excess deaths (UI –65 thousand to 351 thousand). Across the World Bank Income groups, High-income economies account for 2.16 million excess deaths (UI 2.09 million to 2.24 million), Upper-middle-income economies account for 4.24 million excess deaths (UI 4.18 million to 4.31 million). Lower-middle-income economies account for 7.87 million excess deaths (UI 6.30 million to 9.60 million) and Low-income economies account for 638 thousand excess deaths (UI 434 thousand to 846 thousand).