Life's a beach, and then you die

Alternative title for this post: The Sunshine Charnel House

Last week I put up a post illustrating the tremendous lag in Florida's COVID death data.

Most states take a few days to collect their data and get it posted, but after that point their older data stabilize. They're not continually updating numbers that are 10 or 20 days old.

Not Florida. They're special. It's now 25 days since I started watching their death numbers, and they're still going back and adding deaths to data that are two months old.

But they're special in another way as well, and that is simply in the amount of COVID-related death they're producing.

Along the way to illustrating that, I'll give you some pretty good evidence that VACCINES WORK, and also give a sense of how much better we might be doing with a higher vaccination rate.

Back in July I posted a comparison of the Delta surge in a collection of nine not-randomly-chosen states. (I wanted places famously having trouble, like Florida and Missouri, and the state with our highest vaccination rate - Vermont - and then through in some others, including New York, where I live, and Massachusetts, where I grew up and where I still have family.)

Overall, states with higher vaccination rates started their surges later, from a lower level, and weren't rising as fast.

That's still true, but I wanted a more comprehensive measure, that somehow gathered in both how early you started, how high you started, how high you got, and how much time you spent at a very elevated level.

What I settled on was to look at cumulative infections in a state from June 1 through August 30. I measured that by taking total infections recorded as of August 31, and subtracting  total deaths recorded as of June 1.

With that "How was your summer?" question as the main effect, I chose as my causal variable a state's level of vaccination on June 1, at the start of the mess. And I went with "fully vaccinated" rather than "at least one shot" - early in the vaccine roll-out, there was evidence that even the first shot of the mRNA vaccines did a good job of preventing infection, but that with Delta it really took both shots to get a good effect.

So: I'm looking at the relationship between:

1. What was each state's population percentage that was fully vaccinated by June 1st; and
2. What portion of each state's population got infected between then and August 31st.

And that relationship looks like this:

It certainly does appear that states with higher vaccination rates at the beginning of the summer (further to the right on the chart) also had a smaller percentage of their population test positive over the summer (lower down on the chart).

And if you fit a power function to the scatter of points, you get an R-squared of 0.627, suggesting that this single factor - how vaccinated was your state on June 1 - can explain about 63% of the variance in how many people tested positive.

The t-statistic on the vaccination variable is over 9, implying a vanishingly small chance that there is no relationship in the real world, and that the apparent relationship is just random noise falling a certain way.

And the relationship is not merely statistically significant. Its estimated size is also large enough to be meaningful. The country's overall rate of full vaccination by June 1 was 40.7%. The regression predicts that a state with that level of vaccination would see 1.43% of its population test positive over the summer. For a state with 10,000,000 people (roughly Georgia, or North Carolina, among others), that would mean about 143,000 infections over the summer.

If the state had 10 percentage points more vaccination (meaning it was at 50.7%), it's predicted positives over the summer would be 0.83% of its population. Our hypothetical state with 10,000,000 people would see only 83,000 infections - 60,000 fewer than with the average vaccination rate.

As you can see on the figure, the relationship is not linear. The lower your vax rate, the more quickly infections rise. So a state with 10 percentage points less vaccination than average (putting it at 30.7%) would expect an infection rate of 2.89%. In a state with 10,000,000 people, that's 289,000. That's 146,000 more infections than at the average vax rate.

On these charts, you might have noticed one particularly "out there" outlier.

In case you didn't, here's the second chart with the outlier highlighted.

It is 3.1 standardized residuals above its "predicted" value. The next-biggest outlier is only 1.9 standard deviations off. So Florida went into the summer with an almost average vaccination rate, but ended up really punching above its weight, with the second-highest rate of infections and an unbelievably high level given is vax status.

But that's just infections. Where Florida really excels is in COVID deaths.

Here's the chart. The horizontal axis is still percent fully vaccinated by June 1st, but the vertical is now deaths per 100,000 during June-August.

You probably noticed that outlier, but in case you didn't, I've made it easier to see.

Florida is 3.5 standardized residuals above its predicted value, wile the next largest error is 2.3 standardized residuals.

I don't know why Florida excels in death. It could be as simple as having an older population, in which case age-adjusted mortality rates would bring its numbers more in line with the other states.

Hypotheses are welcome.