COVID Excess Mortality Percentage, Racial/Ethnic Disparities in COVID Mortality, and Vaccine Effectiveness: Evidence from Linked Mortality and Vaccination Records

Abstract

COVID-19 mortality rates rise strongly with age, but so do other natural causes of death. We develop a new measure of the COVID-19 mortality burden, the COVID Excess Mortality Percentage (CEMP), defined as COVID-19 deaths as a fraction of all deaths from natural causes other than COVID. We use this measure to study COVID-19 mortality in Indiana and Wisconsin, including racial/ethnic disparities in mortality rates. We find very high disparities, especially in 2020, with CEMP ratios for Hispanics to non-Hispanic Whites as high as 9:1 for ages 50-59. We find very different CEMP patterns by age and race/ethnicity, in the pre-vaccine period (2020) and the vaccine-available period (April 2021-March 2022).

We also report data on vaccine effectiveness (VE) in Milwaukee County, where we can link individual death records to vaccination records. Measuring VE based on CEMP controls for the potential for the vaccinated to be healthier and hence face lower COVID mortality risk without vaccination. VE measured this way is substantially lower than reported in many other studies (e.g., 60% for fully vaccinated (but not boosted) adults during 1Q 2022 (Omicron-dominant period) and 71% during 4Q 2021 (Delta-dominant period). Three-vaccine-dose VE is much higher, at around 90%, and similar for Moderna and Pfizer, but COVID mortality risk after two Pfizer doses is over twice the two-dose Moderna risk. The gap between two-dose and three-dose VE implies that tens of thousands of COVID decedents would likely have survived with a faster booster rollout.

The Online Appendix for this paper is available at http://ssrn.com/abstract=3706517

Note:
Funding Information: This project was funded by the National Institutes of Health, award 3 UL1 TR001436-06S1.

Conflict of Interests: The authors have no competing interests.

Ethical Approval: Approved by the Medical College of Wisconsin Human Research Review Board.