Weekly Update: Right on schedule, the partisan case rate divide has started reverting to form, with death rates likely to follow soon.


For months I posted weekly looks at the rate of COVID-19 cases & deaths at the county level since the end of June, broken out by partisan lean (i.e, what percent of the vote Donald Trump received in 2020), as well as by the vaccination rate of each county in the U.S. (nonpartisan).

This basically amounts to the point when the Delta Variant wave hit the U.S., although it had been quietly spreading under the radar for a few months prior to that.

Now that we're a full seven weeks into the Omicron Variant wave, I've updated my case/death rate tracking to reflect that as well...because the data so far is showing a completely new chapter as we enter the 3rd year of the Coronavirus Pandemic.

The "start" of the Delta Wave was easy to lock in for my purposes; both cases and deaths from COVID had dropped off dramatically right up until around the end of June. The Delta Wave started showing up in the daily deaths pretty quickly as July started. The transition from the Delta to Omicron was a lot fuzzier, but I've decided to go with December 15th as my transition point.

As always, here's my methodology:

Remember: "Decile" means 1/10th or 10% of the total population (all 50 states + DC).

Here's the final ratios for the Delta wave (6/15/21 - 12/15/21):

  • Delta wave CASE rates: 2.46x higher in the reddest decile than the bluest decile
  • Delta wave DEATH rates: 5.77X higher in the reddest decile than the bluest decile
  • Delta wave CASE rates: 2.12 higher in the least-vaccinated decile than the most-vaccinated decile
  • Delta wave DEATH rates: 4.77x higher in the least-vaccinated decile than the most-vaccinated decile

What about Omicron?

First, the partisan breakout: The case rate ratio is a very different picture under Omicron. For the first six weeks of Omicron, case rates are 1.23x higher in the bluest decile than the reddest. It's worth noting, however, that this is down from 2.2x higher only a month earlier:

Death rates since Omicron started still swing red, as the death rate in the reddest decile is 1.74x higher than in the bluest. This is down from 2.9x higher a month earlier, however, and down from nearly 5.8x higher during the Delta wave. Remember, deaths tend to lag new cases by about 3 weeks, so it actually makes sense that the two would be shifting in opposite directions at the moment:

It's a similar story with the nonpartisan vaccination rate ratios:

Case rates since mid-December are now 1.43x higher in the most-vaccinated counties...except that this is down from 2.4x higher a month earlier:

The death rate, however, is still 2.16x higher in the least-vaccinated decile than the most. This is down from 3.3x higher a month ago, and way down from the 4.8x higher ratio during the Delta wave...but it's up slightly from last week:

Here's what all four of the ratios above look like over time; the lines compare the Reddest vs. Bluest Deciles and the Least- vs. Most-Vaccinated Deciles. As you can see, the case rate ratios (at the bottom) are slowly moving back up to the 1:1 threshold again, while the drop in the death rate ratio has either flattened out (partisan lean line) or nearly done so (vaxx rate line).

What's also remarkable is how closely the two different criteria mirror each other every step of the way:

This shift over time is even more obvious (at least on the case rate side) when I go back to June 30th. As I recently noted, by mid-January, Omicron had almost completely cancelled out the "Red/Blue divide" in terms of cumulative case rates since June, which had reached as high as a 3:1 ratio before starting to recede...but the death rate was still 4x higher in the reddest counties in the U.S. than the bluest as recently as a couple weeks ago.

As noted above, that's still dropping (it's down to around 3.5x higher through this week), but the rate of that drop has slowed substantially. Again, given the 3 week lag between cases and deaths (give or take), I'd expect the red line below to start reversing itself and moving back upwards again in another 2-3 weeks:

However, I don't expect to see anything close to the 6:1 ratios we saw during Delta; it'll probably hit perhaps 3:1 or so by May or June, I'd imagine.

In the meantime, get vaccinated & get boosted, dammit.