Retrospective study estimates the substantial number of COVID-19 deaths among the unvaccinated

By Sangeeta PaulReviewed by Danielle Ellis, B.Sc.Feb 15 2022

In a recent study posted to the medRxiv* preprint server, researchers from the United States (US) performed a retrospective analysis to estimate excess coronavirus disease 2019 (COVID-19)-associated deaths in the unvaccinated population of the US.

According to the World Health Organization (WHO), COVID-19 has caused 905,957 deaths in the US to date. The authorization for vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was granted in late 2020 in the US, and the vaccines proved to be efficacious in preventing COVID-19-associated deaths. A total of 527,784,089 SARS-CoV-2 vaccination doses have been administered in the US so far. However, many individuals remain unvaccinated due to various reasons.

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

This study was designed to measure the magnitude of deaths associated with COVID-19 in the unvaccinated populations of the US.

Study design

In the current work, the team used The Weekly, which was available on US Centers for Disease Control and Prevention (CDC), and aggregated the data from 26 participating US jurisdictions. The data included age-wise COVID-19-associated death rates and status of vaccinations. COVID-19-associated death was defined by any death in individuals who had a documented positive SARS-CoV-2 diagnosis.

The participating jurisdictions included Alabama, Arkansas, Arizona, California, Connecticut, Colorado, District of Columbia, Florida, Georgia, Idaho, Indiana, Kansas, Louisiana, Massachusetts, Minnesota, Michigan, Nebraska, New Mexico, New Jersey, New York City, Rhode Island, Washington, Texas, Utah, and Wisconsin.

Using the data, the team estimated the excess death figures that might have been averted with vaccination among the age group of >18 years of the unvaccinated population between May 30, 2021, and December 4, 2021. To estimate the death rate per week, which can be an attributable factor for non-vaccination, researchers performed a subtraction of the death rate in the vaccinated from the rate of the unvaccinated population.

Further, to measure the excess death in the unvaccinated population, the researchers multiplied the rate difference for each age group for each week by the number of people in the unvaccinated group. Through the US 2020 Population Census estimates, the researchers extrapolated the death numbers owed to non-vaccinations in the 26 participating jurisdictions to the overall population of the US.

Findings

The results showed that between May 30, 2021, and December 4, 2021, in all the 26 US jurisdictions analyzed, there was an excess of 83,400 deaths among the unvaccinated population. More than 34% of total excess deaths occurred in the age group of 65-79 years, followed by 31% in the age group 50-64 years.

Based on the national vaccination rate data, the researchers excluded the partially vaccinated population and extrapolated the estimate to the US population. Approximately 135,000 excess deaths were observed in the age group of  >18 years old.

During the sensitivity analysis, the researchers observed that in the non-26 jurisdictions, excess deaths dropped to 119,000 if there were a 30% lower unvaccinated population and increased to 150,000 if there was an assumed 30% higher unvaccinated population for the rest of the country.

Further excess death rates also varied with the proportion of the partially vaccinated population.

Conclusion

To summarize, the findings of this study stipulated that there was a considerable increase in the number of COVID-19-associated deaths in the unvaccinated population in the US and highlighted the significance of vaccinations against SARS-CoV-2 infections to prevent further irrelevant mortality during this COVID-19 pandemic.

However, the current study has some limitations. The analysis considered excess deaths only between May 30, 2021, and December 4, 2021, while many excess deaths had occurred before and after this period. So the estimates provided were underestimates of excess death that had occurred since the availability of vaccines. Also, the study only measured the direct effects of vaccination, while indirect effects could aggravate excess death numbers since vaccines are more likely to curtail transmission to others.

*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.