The World Health Organization has a mandate to compile and disseminate statistics on mortality, and we have been tracking the progression of the COVID-19 pandemic since the beginning of 20201. Reported statistics on COVID-19 mortality are problematic for many countries owing to variations in testing access, differential diagnostic capacity and inconsistent certification of COVID-19 as cause of death. Beyond what is directly attributable to it, the pandemic has caused extensive collateral damage that has led to losses of lives and livelihoods. Here we report a comprehensive and consistent measurement of the impact of the COVID-19 pandemic by estimating excess deaths, by month, for 2020 and 2021. We predict the pandemic period all-cause deaths in locations lacking complete reported data using an overdispersed Poisson count framework that applies Bayesian inference techniques to quantify uncertainty. We estimate 14.83 million excess deaths globally, 2.74 times more deaths than the 5.42 million reported as due to COVID-19 for the period. There are wide variations in the excess death estimates across the six World Health Organization regions. We describe the data and methods used to generate these estimates and highlight the need for better reporting where gaps persist. We discuss various summary measures, and the hazards of ranking countries’ epidemic responses.

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Estimating the true mortality burden of COVID-19 for every country in the world is a difficult, but crucial, public health endeavor. Attributing deaths, direct or indirect, to COVID-19 is problematic. A more attainable target is the "excess deaths", the number of deaths in a particular period, relative to that expected during "normal times", and we estimate this for all countries on a monthly time scale for 2020 and 2021. The excess mortality requires two numbers, the total deaths and the expected deaths, but the former is unavailable for many countries, and so modeling is required for these countries. The expected deaths are based on historic data and we develop a model for producing expected estimates for all countries and we allow for uncertainty in the modeled expected numbers when calculating the excess. We describe the methods that were developed to produce the World Health Organization (WHO) excess death estimates. To achieve both interpretability and transparency we developed a relatively simple overdispersed Poisson count framework, within which the various data types can be modeled. We use data from countries with national monthly data to build a predictive log-linear regression model with time-varying coefficients for countries without data. For a number of countries, subnational data only are available, and we construct a multinomial model for such data, based on the assumption that the fractions of deaths in sub-regions remain approximately constant over time. Our inferential approach is Bayesian, with the covariate predictive model being implemented in the fast and accurate INLA software. The subnational modeling was carried out using MCMC in Stan or in some non-standard data situations, using our own MCMC code. Based on our modeling, the point estimate for global excess mortality, over 2020-2021, is 14.9 million, with a 95% credible interval of (13.3, 16.6) million. This leads to a point estimate of the ratio of excess deaths to reported COVID-19 deaths of 2.75, which is a huge discrepancy.

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).