Yale Daily News

With COVID-19 vaccine hesitancy largely split along party lines in the United States, a study published by three Yale professors suggests a link between partisan affiliation and death rates during the COVID-19 pandemic.

In a working paper published by the National Bureau of Economic Research, Jacob Wallace, assistant professor of public health (health policy) at the School of Public Health, Jason L. Schwartz, associate professor of public health (health policy) at the School of Public Health, and Paul Goldsmith-Pinkham, assistant professor of finance at the School of Management, explored the link between voters’ political affiliation and excess death rate throughout the COVID-19 pandemic.

Looking at voters in Ohio and Florida, the researchers measured excess death rates between registered Republican and Democratic voters, or the percent increase in deaths above expected deaths given specific seasonality, geographic location, party affiliation and age. The study found that, between 2018 and 2021, the excess death rate for Republican voters was 5.4 percentage points, or 76 percent higher, than that of registered Democrats. The majority of the difference, though, was concentrated after the introduction of COVID-19 vaccines: after vaccines became available, the death rate gap between Republicans and Democrats widened from 1.6 percentage points to 10.4 percentage points.

“Our results build on an important, prior literature that documented that Republican-leaning counties have had higher COVID-19 mortality rates than Democratic-leaning counties,” Wallace wrote to the News. “However, to our knowledge, we are the first to demonstrate that there exists a link between political party affiliation and excess death rates during the COVID-19 pandemic at the individual level.”

Wallace had collaborated previously and separately with both Schwartz, a vaccine policy expert, and Goldsmith-Pinkham, a specialist in econometrics. A broader collaboration to explore the association between political party affiliation and excess deaths, he notes, was “natural.”

The team examined the deaths and 2017 voting records of 577,659 individuals who died between January 2018 and December 2021 of age 25 or older. By analyzing excess death rates specifically, the researchers were able to control for disparities in death rates linked to other factors, such as age, season or location of residence.

A figure from the working paper illustrating partisan disparities in COVID-19 excess death rates over time. 

“Republican- and Democratic-leaning counties differ on many dimensions so it can be difficult to attribute differences in COVID-19 mortality to political party affiliation rather than other factors that differ at the county-level,” Wallace wrote. “Our comparisons are adjusted for differences in excess death rates by age and county, and so can be thought of as demonstrating that Republican voters have higher excess death rates than Democratic Voters of the same age that reside in the same counties as them.”

Their analysis suggests a higher excess death rate for Republican voters than Democratic voters, with the difference spiking after COVID-19 vaccinations became widely available. Moreover, those differences were concentrated in counties with lower vaccination rates: at time points after the introduction of the COVID-19 vaccine, the study identified higher excess death rates for Republicans in counties with lower vaccination rates.

In contrast, the difference in excess death rates between voters of each party was “nearly zero” in counties with the highest vaccination rates, according to the study. This indicates smaller death disparities in “areas with larger take-up of vaccines.”

“[The] results suggest that the well-documented differences in vaccination attitudes and reported uptake between Republicans and Democrats have already had serious consequences for the severity and trajectory of the pandemic in the United States,” the paper continued. “If these differences in vaccination by political party affiliation persist, then the higher excess death rate among Republicans is likely to continue through the subsequent stages of the COVID-19 pandemic.”

Jacob Hacker, the Stanley B. Resor Professor of Political Science, was forwarded the paper by his coauthor. According to Hacker, the analysis is “very important” within the field, since it demonstrates that the “well-known association” between county partisanship and excess death rates applies at an individual level as well.

The paper also makes a strong case, Hacker continued, that the difference is due to variation in vaccination rates after the vaccine’s public release.

Howard Forman, a professor of radiology, economics, management and public health who was not involved in the study, concurred, adding that the findings represent a “more rigorous way” of showing that Republican counties in the two states performed “worse” than Democratic counties.

“It is sadly an example of just how polarized we are as a nation,” Forman said. “That something that shouldn’t be so related to our political affiliation is unfortunately, incredibly identified with our political affiliation.”

Yet the lack of a large mortality difference before vaccines were available came as a surprise to both Hacker and Forman. The increase in excess death rate after the vaccine’s development indicates that differences in distancing and masking behavior, which “seemed to be influenced by partisanship,” were apparently “not enough to make a big difference” to mortality, according to Hacker.

Hacker also expressed concern about aspects of the paper’s methodology. The study, for instance, only examines two states, and the researchers utilize county-level vaccination trends rather than individual-level data on vaccination. Moreover, while Hacker commends the paper’s use of excess death rates, he added that, ideally, a study would use “a bunch of demographic variables to give you a baseline death rate.”

The excess death rate metric also may not account for the fact that ‘excess deaths’ could be attributed to strains on the healthcare system that resulted in the loss of lives for patients without COVID-19, according to Hacker.

“Still, the case for thinking that partisanship influences vaccination is strong, and so too is the case for thinking that vaccination influences death rates,” Hacker wrote to the News. “I think they add a lot of specific evidence to back up those highly plausible arguments.”

Moving forward, the researchers hope to develop a more comprehensive study to examine the relationship between partisanship and COVID-19 mortality. According to Wallace, they hope to obtain national level voter data to conduct a follow up of the two-state study.

That dataset would allow the researchers to examine partisanship and COVID-19 nationally, while enabling them to explore why different regions may have differences in the party-death disparity.

“Having data on voters in a broader set of states would also allow us to explore the area-level correlates of excess mortality differences associated with political party affiliation,” Wallace wrote. “Said another way, we could try to understand whether there are place-based policies or other characteristics of places that predict whether Republican or Democratic voters will have higher excess death rates.”

The Pfizer-BioNTech COVID-19 Vaccine has been available under EUA in individuals above 16 years of age since Dec. 11, 2020.

Giri Viswanathan is a Science and Technology editor for the News. Previously, he covered the Yale School of Public Health and was also a Photography Editor. Originally from Pittsburgh, PA, Giri is a junior in Timothy Dwight College majoring in Global Affairs as a Global Health Scholar.