Conflicting COVID-19 excess mortality estimates

Excess mortality is an important metric summarising COVID-19 disease burden, informing public health policy and future preparedness needs.¹ However, separating the deaths that occurred from COVID-19 versus those from all other causes is challenging. Essentially, the unknowns are the counterfactual, should an infection wave not have happened. A solution to this challenge is to estimate expected number of individuals who would have died and compare this with the observed number of deaths. The estimation of expected number of deaths must consider changes in population and seasonal dynamics and be based on an appropriate reference period. The COVID-19 Excess Mortality Collaborators² present an important study that estimates 18·2 million excess deaths spread across 191 countries and territories in the first 2 years of the COVID-19 pandemic, 2020 and 2021. The authors use an ensemble-based approach to estimate global excess mortality due to data paucity in many countries. Although this global estimate might be broadly correct and serves as an important reminder of the effect of COVID-19, we strongly caution against the over-interpretation of the constituent country estimates. For European countries, we instead recommend the use of EuroMOMO—a standard and coordinated approach for mortality monitoring in Europe. EuroMOMO estimates expected excess mortality, correcting for delay in registration and changes in population and seasonality during a 5-year reference period.³ EuroMOMO excess mortality estimates include both surplus and deficit mortality, with deficit mortality expected under stringent control restrictions. Whether the COVID-19 Excess Mortality Collaborators² consider both surplus and deficit mortality is unclear.

We find conflicting estimates of excess mortality for several countries with reliable and near complete mortality reporting. For example, for Denmark, the authors² predicted an excess mortality of 203% higher than the estimate from EuroMOMO. The trend in increasing excess mortality in the later part of 2021 estimated by the study² is inconsistent with trends reported from the Danish health authorities, the total mortality, and the EuroMOMO excess mortality. The COVID-19 Excess Mortality Collaborators² do not provide details on these discrepancies and do not provide their weights and background estimates for all countries. Because of the inconsistencies shown in our table (appendix p 1), we caution both the use and over-interpretation of individual country estimates from the study.² Although the estimates from this study² are important in a global perspective, for individual countries with good health-care reporting, nationally reported estimates (eg, from EuroMOMO) are probably more reliable.

For more on EuroMOMO see: https://www.euromomo.eu/]

We declare no competing interests.