Amid the pandemic, Republican voters in Ohio and Florida had a significantly higher rate of excess deaths after the nationwide rollout of COVID-19 vaccines compared with those who voted Democratic, according to a study published this week in JAMA Internal Medicine.

As the pandemic coronavirus spread between March 2020 and April 1, 2021, people from both parties saw similar surges in excess deaths—that is, deaths above what would be expected had there not been a global health crisis. But after April 1, when all adults in both states were eligible for vaccination, a gap emerged in the rate of excess deaths between Republican and Democratic voters. Republicans had an excess death rate 7.7 percentage points higher than their blue counterparts, amounting to a 43 percent difference in the excess death rates.

The study is just the latest to find a connection between political party affiliation and deaths during the pandemic. But, it takes the connection a step further, going beyond county-level political leanings and looking at how party affiliation linked to deaths at the individual level. The authors—all researchers at Yale University—focused on Ohio and Florida because those were the only two states with readily available public data on voter registration.

The study involved death data on 538,159 people in Ohio and Florida, age 25 and older, and their linked voter registration files. The researchers did not have complete data—the linked data didn't contain a cause of death or vaccination status. But, they could evaluate excess weekly deaths by age, state, county, and party affiliation. They found that the gap in excess deaths was larger in counties with lower vaccination rates, suggesting that lack of vaccination among Republican voters may partly explain the higher death rates.

Thus, they concluded "well-documented differences in vaccination attitudes and reported uptake between Republican and Democratic voters may have been factors in the severity and trajectory of the pandemic."

But, of course, there are limitations. Political affiliation may be a proxy for other underlying risk factors, including medical conditions or socioeconomic status (although the gap in excess death rates only appeared after the vaccine rollout). The adherence to other health measures—social distancing and masking—may also contribute to the political divide. The researchers suggest more research will need to detangle all the possible factors.

In the meantime, they suggest that the increased health risks to Republicans could continue as the pandemic virus carries on. Although over 270 million Americans (81.4 percent) have received at least one dose, more than 50 million adults have not completed a primary series, putting them at higher risk of death and severe disease. Public health efforts moving forward should focus not just on booster campaigns for the vaccinated but also on addressing vaccine hesitancy and refusal among the unvaccinated. So far, over 1.1 million people in the US have died from COVID-19.