A Blog by Jonathan Low


May 21, 2021

Why Blue States May Reach Covid Herd Immunity Sooner Than Red States

The data reveal that the pace of vaccination in the US  is strongly correlated with political leaning. JL 

Craig Helmstetter and Kristine Liao report in APM Research Lab:

It is well-documented that Republicans are more likely to be hesitant of getting vaccinated for COVID-19 than Democrats are. It is now apparent vaccine hesitancy, especially among conservatives may slow the progress of entire states, and regions. As of April 25, 37% of the population in states that voted for Trump are vaccinated, compared to 46% in states won by Biden. Trump-won states would require another 5.8 months to reach the 85% target. Biden-won states would reach the 85% vaccinated threshold in under four months. The pace of vaccination is correlated with political leaning.

Over the last few weeks the United States’ progress on vaccinating its population against COVID-19 has slowed, as have the associated prognostications as to when the country will reach herd immunity—or even whether we will ever reach the level of vaccination necessary to be functionally free of the virus. Given the initial excitement and high demand for vaccination, we sought to find why things have slowed down.

While issues related to the use and production of Johnson & Johnson’s COVID-19 vaccine have contributed to the slowdown, it is becoming more apparent that politics are at least partly to blame. And by politics we don’t mean a deep-state conspiracy that is secretly channeling vaccines to some elite cabal. We simply mean whether people lean Democrat or Republican.

It is well-documented in public opinion polling that Republicans are more likely to be hesitant of getting vaccinated for COVID-19 than Democrats are (see box below). But it is now becoming apparent that this difference is not just a matter of personal preference—vaccine hesitancy, especially among conservatives may slow the progress of entire states, and even entire regions of the country, toward greater health and safety.


  • According to the April Marist poll, 44% of Republicans say they would choose not to be vaccinated, compared to 26% of independents and only 7% of Democrats. Even more dramatically, half of those who supported Trump in the 2020 election said they would avoid getting vaccinated, compared to only 5% of those who supported Biden.

  • The March Kaiser Family Foundation poll found that 29% of Republicans say they would definitely not get the vaccine, compared to 5% of Democrats.

  • According to the February Pew Research poll, Democrats are now 27 percentage points more likely than Republicans to say they plan to get or have already received a COVID-19 vaccine (83% to 56%)—a gap wider than those seen at multiple points in 2020.

  • In the January AP-NORC poll, 44% of Republicans said they probably or definitely will not receive the vaccine, compared to 18% of Democrats.

Based on our analysis of federal data, states that favored former President Trump in the 2020 election generally have lower COVID-19 vaccination rates, and those that favored President Biden have higher vaccination rates. This is obvious from eyeballing the maps below, as well as through comparing the averages: As of April 25, on average, 37% of the population in states that voted for Trump are vaccinated, compared to 46% of the population in the states won by Biden. 

There are exceptions: the most vaccinated Trump-won state, South Dakota (44%) has a higher vaccination rate than the Biden-won states of Georgia (34%), Nevada (38%), Arizona (40%) and Michigan (41%). Still, the overall trend is clear, with a strong 0.67 correlation coefficient between the state-level vaccination rate and Biden’s margin of victory (or loss) in each state. In plain terms: generally speaking, the greater Biden’s margin of victory, the higher the percentage vaccinated and the greater Trump’s margin of victory, the lower the percentage vaccinated.

When we use states’ current progress to project one possible marker of herd immunity—an 85% vaccination rate—the gulf in current vaccination rates turns into potential months of waiting until life can return to some semblance of normalcy. On average, Trump-won states would require another 5.8 months to reach the 85% target, ranging from a low of four months in South Dakota to a high of eight more months in Mississippi. 

In this same scenario, which doesn’t account for possible slow-downs related to approvals for use of vaccines among children, Biden-won states would average reaching the 85% vaccinated threshold in just under four months. New Hampshire would get there in only two months! 

Based on our analysis, it’s evident that the pace of states’ COVID-19 vaccination progress is correlated with their political leanings. But whether partisanship itself is the cause for vaccine hesitancy is less obvious. The Kaiser Family Foundation poll found that 20% of Republicans said they would be more likely to get vaccinated if former President Trump strongly urged them to do so, suggesting that political ideology alone may not be the central cause of hesitancy.

It must also be noted, however, that conservative opposition to vaccination pre-dates anti-vaccination views associated with Trumpism. For example, a decade ago Matthew Baum found that swine flu vaccination rates similarly varied along partisan lines.

More recently, among the respondents to the KFF poll who said they would definitely not get the vaccine, the most common reason they cited, at 17%, was that the vaccines are too new and not enough information is known about their long-term effects. In addition to these fears, a sensitivity for individual liberty and lack of trust in government and authority could be other key drivers of vaccine attitudes, especially in rural, Republican, deeply Christian communities, according to a recent New York Times article.

Finally, while we are well aware of the racial and ethnic disparities in COVID-19 vaccination rates, that now appears to be much more of an issue of access than of personal hesitancy; more a symptom than a cause of the slowdown in vaccination rates. In April, for example, the Marist Poll found little to no difference in vaccine hesitancy along racial or ethnic lines, with 23% of Whites and 26% of “non-Whites,” including 25% of Black Americans and 31% of Latino Americans, indicating they would avoid getting vaccinated.

Convincing the most vaccine hesitant of the U.S. population to get the shot will be a major challenge in the months to come. As variants of the virus are already devastating India and countries in South America, the failure to reach across political differences could forestall the health and wellbeing of the entire nation.


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