The number of new coronavirus cases recorded in the United States has doubled over the past two weeks, with nearly 56,000 people contracting the virus each day. That’s higher than at any point since late April, and it is higher than at any point before mid-July 2020 (though limited testing early that year kept numbers down).

What’s different about the pandemic at the moment, of course, is that every American teenager and adult has access to a vaccine that can largely prevent infection in the first place (not to mention “hospitalizations,” as a White House slide had it Tuesday). But after a steady increase in vaccinations, the effort to protect the public has largely stalled, leaving millions of Americans at risk. Had the United States seen far more vaccinations two months ago, we would almost certainly be seeing far fewer new cases now.

But that vaccination effort has been hampered by broad hesitance, particularly among Republicans. From the outset of the pandemic, Republicans have been less likely to say they intend to be vaccinated, and in the months since then, those views have been matched by actual vaccination rates. When we talk about the unvaccinated population that is at risk, in other words, we’re often talking about Republicans who’ve chosen not to be vaccinated.

That, too, is reflected in the data. In the past two weeks, there have been about 237,000 new coronavirus cases recorded in counties that voted for President Biden last year — and 388,000 in counties that voted for Donald Trump. Adjusted for population, there have been about 126 new cases per 100,000 residents of blue counties and 278 new cases per 100,000 residents of red ones. On average, blue counties are seeing 10.2 new cases for every 100,000 residents, while red counties are seeing 19.5 new cases per 100,000 residents.

If we break every county in deciles of 2020 vote and rates of completed vaccinations — that is, 10 groups of about 300 counties apiece, ranked by vote or vaccination levels — we can see how partisanship and vaccination levels overlap.

Here, for example, is the average number of new cases per resident on those two metrics. Notice that the graph at left goes from more pro-Biden to more pro-Trump, and the graph at right goes from least to most vaccinated.

If you’re curious about the data at the level of specific counties, this interactive visual has you covered.

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0 to 25.2%
 
25.3 to 33.8%
 
33.9 to 42.7%
 
42.8% or higher
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It’s useful to note, though, that the increase in cases has been more uniform. In other words, most counties have been trending up over the past two weeks, so the degree at which new cases changed is not as obvious.

What is more obvious is if we compare where counties are now with where they were a year ago. More pro-Trump and less-vaccinated counties have generally seen bigger increases in cases relative to a year ago — before vaccines were available.

One outlier is that group of the most-vaccinated counties, seen in the column at far right on the right-hand graph above. That’s in part because places such as New York City have seen a recent increase in cases, while last summer they kept case totals low.

But New York and other metropolitan areas are also affected because they have a lot of people. Vaccinate 40 percent of a town with a population of 10,000, and you have 6,000 unvaccinated people walking around. Vaccinate 95 percent of a city with a population of 5 million, and there are 250,000 unvaccinated people walking around.

In a Twitter thread posted Monday, Bob Wachter, chair of the University of California at San Francisco Department of Medicine, noted that this was the problem his city was seeing. Cases are increasing quickly, thanks largely to the highly contagious delta variant. Wachter had written an essay for this newspaper in April calling it the most dangerous time for the pandemic in the United States.

“I was wrong,” he said Monday — “now is even MORE dangerous since Delta has taken over, caution’s been thrown to the wind, and there’s far more virus around.”

His thread ended by noting that “the politics are hard” when it comes to vaccination. That’s indisputably true. But it is also remarkable — and depressing — the extent to which those politics are discernible in our coronavirus data.