New study highlights the under-reporting of COVID-19 deaths in the US

By Dr. Sanchari Sinha Dutta, Ph.D.Reviewed by Aimee MolineuxJan 19 2023

A study conducted by US-based scientists highlighted that a considerable percentage of coronavirus disease 2019 (COVID-19)-related deaths remained unreported in different counties across the United States.

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

The study is currently available on the medRxiv* preprint server.

Background

Excess mortality is a widely used measure to assess the mortality impact of the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The difference between the reported deaths in a given period and the expected deaths based on pre-pandemic mortality trends in the same period is regarded as excess mortality.

The number of excess deaths officially not assigned to COVID-19 can exceed the reported number of deaths assigned to COVID-19 on death certificates. This could be due to several factors, including the failure of certifiers to recognize COVID-19-related deaths clinically. Personal or political beliefs could also influence assigning deaths to COVID-19 on certificates.

Many comorbidities and atypical symptoms of COVID-19 can make it difficult to identify the real cause of death. Deaths caused by pandemic-related delays or interruptions in healthcare access or socioeconomic crisis could be indirectly related to the pandemic. All these factors could collectively impact the actual death toll of the pandemic.

In the current study, scientists have compared the estimates of monthly excess mortality and the estimates of reported COVID-19 deaths in counties across the United States during the first two years of the pandemic.

Study design

Scientists have developed a Bayesian hierarchical model to estimate the monthly all-cause excess mortality for 3,127 counties from March 2020 to February 2022. They used publicly available pre-pandemic data (January 2015 - December 2019) to predict excess mortality.   

They used relative estimates of excess mortality to compare excess mortality and COVID-19 mortality across counties with different populations and numbers of deaths. Relative excess mortality was derived by dividing the number of excess deaths by the number of expected deaths in a given area.

Important observations

According to the study estimations, about 1,134,364 excess deaths occurred in the United States during the first two years of the pandemic. Of these deaths, 866,187 were assigned to COVID-19, and 268,176 were not assigned to COVID-19. These estimates indicate that about 24% of excess deaths were not assigned to COVID-19 in the United States during this period.

The relative excess deaths not assigned to COVID-19 were higher in non-metro counties than in small, medium, or large metro counties. The excess mortality not assigned to COVID-19 was highest in the Mountain division and the South.  

Except for the New England and Middle Atlantic divisions, all Census divisions had more excess deaths than COVID-19 deaths. COVID-19 mortality exceeded excess mortality for these two divisions in all metro counties.

In areas with the highest number of excess deaths not assigned to COVID-19, excess deaths occurred more frequently during the peaks of reported COVID-19 deaths. In contrast, a stable rate of excess deaths not assigned to COVID-19 was observed in areas with higher COVID-19 mortality than in excess mortality.

Among included counties, Shelby, Tennessee, had 2.4 times higher excess mortality than COVID-19 mortality during the first two years of the pandemic. This was equivalent to 4,014 excess deaths that were not assigned to COVID-19.

Similarly, Lafayette, Louisiana, had 2.5 times higher excess deaths than COVID-19 deaths during the first two years of the pandemic. This was equivalent to 654 excess deaths that were not assigned to COVID-19.

Study significance

The study predicted the monthly excess all-cause deaths for US counties and identified that about 24% of all excess deaths were not assigned to COVID-19 during the first two years of the pandemic. Non-metro counties were less likely to attribute excess deaths to COVID-19 on death certificates officially.

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.