Wed 2021-Mar-10

Republicans vs Herd Immunity

Tagged: COVID / MathInTheNews / Politics / SomebodyAskedMe

If a large enough clade of US persons refuse COVID-19 vaccination, herd immunity may never be reached. Right now in the US, that clade seems to be White Republicans. (World-wide, it’s of course more complicated.)

Vaccine hesitancy in the US by subgroups

Somebody asked me what I thought about vaccine hesitancy in various groups, and how that would affect our attempt to reach herd immunity.

Everybody talks about Blacks, who actually have pretty good, rational reasons to think the medical system doesn’t have their best interests at heart. But, as we wrote in a previous post, that’s a bit of a red herring according to Axios [1]:

"Axios: White Republican vaccine hesitancy"

We see that the most problematic clade is White Republicans, not Blacks or Latinos. In fact, the Black and Latino vaccine resistance has been trending downward over time, with a nice step down on the day vaccinations started. White Republicans, on the other hand, had a step up in vaccine resistance when vaccines came out, and no noticeable downward trend (red curve). So if you really want to combat resistance and get to general immunity, White Republicans are where you have to start.

That’s why I was so impressed with Dolly Parton’s vaccination video (aside from the intimidating new sobriquet “chicken squat”): her fan demographic skews rural, White, and Republican, so her message was exactly on target.

Is that your only evidence?

As St Thomas Aquinas (or possibly St Augustine?) is alleged to have said, “hominem unius libri timeo” (I fear the man of one book, i.e., someone with narrow views likely to be fanatical). So do we have multiple sources beyond Axios above?

WaPo: 1/3 of Republicans definitely won't get vaccinated WaPo: malicious compliance fishnet mask at CPAC Unfortunately, yes.

From a Washington Post article by Dan Diamond comes the disappointing news that almost 1/3 of Republicans say the “definitely won’t” get vaccinated. [2] The article reports on a number of interviews with some very peculiar people subscribing to various dingbat ideas about vaccines.

My first reaction was “How can anybody be that stupid? “ But then, I looked at the photo at the top of the article. It shows a knucklehead at CPAC showing off his “fishnet mask”, i.e., allowing him to claim to be masked but making the mask utterly useless. This is what’s called malicious compliance, i.e., technically obeying the mask-wearing rule while contemptibly endangering everyone.

So… the Well of Stupid is deep indeed.

Also, the Kaiser Family Foundation reports polling from last December [3] (the whole report is worth a deep read, for related things like factually wrong beliefs about masks) which confirms that the most resistant clade tends to be Republican and less educated:

"Kaiser Family Foundation: resistance skews low education and Republican"

The critical question

Ok, so some people are self-destructively stupid. But does that really endanger others? Are there enough of them to mess up herd immunity so this never goes away?

First, let’s get a handle on the size of the problem. We’ve seen Axios claim 56% of White Republicans, and now the WaPo claim 33% of all Republicans. Let’s go with the lower figure, just to make sure I’m not stacking the deck here. Let’s say about half the US is Republican (alas), so that means we have a hard-core vaccine resistance population of about 0.33 * 0.50 * 100% = 16.5%. That squares roughly with the 15% from the Kaiser Foundation report, above.

Second, let’s look at the mathematical basis for herd immunity. Everything depends on the parameter $R_0$, the basic reproduction number of the disease: the number of new infections caused by each infected person in conditions of perfect mixing. Let $S$ be the fraction of the population who are susceptible. At the critical point where herd immunity sets in, each case generates less than enough new cases to replace it:

\[R_0 \cdot S \leq 1\]

Now let $p$ be the probability a person accepts the vaccine. Then $S = 1 - p$. Plug that into the previous equation and solve for $p$ to get:

\[p \geq 1 - \frac{1}{R_0}\]

Now, for COVID-19, the best estimates for $R_0$ range around 2.5 – 4. [4] [5] The B.1.1.7 and B.1.351 variants might be quite a bit higher, so the upper end of that range is the thing we have to shoot for. That means we need 100% * (1 - 1/4) = 75% of the population vaccinated to get to herd immunity. (At least. New variants may be more virulent, i.e., have a higher value of $R_0$, thus needing a higher vaccination fraction.)

So… we have 25% or less slack in the population who can resist the vaccine and not mess it up for the rest of us. Having 17% of the population being vaccine resisting Republicans isn’t immediately fatal… only if we get near-perfect vaccine acceptance everywhere else, and the new variants aren’t even more virulent. They’re burning up the margin of safety in the name of… knuckleheadery?!


There is precedent for what to do here: Jacobson v Massachusetts (197 U.S. 11 (1905)) is a Supreme Court precedent saying that yes, it is possible for the state to use police powers to compel vaccination (smallpox, in this case). It’s not some dusty old legal peculiarity, either. It gets frequently used as a precedent because it both strengthens and limits police power: you can be arrested & fined for not being vaccinated, but the cops can’t just hold you down and jab you against your will.

And we haven’t even begun to think about the developing world! Unless COVID is eradicated everywhere, it will continue to evolve mutant forms that are more virulent or more deadly. Worst of all would be an “escape mutation” that evades the existing vaccines; then we’d have to start all over again. So we really have to vaccinate pretty much everybody: nobody is safe until everybody is safe.

Sometimes, that’s what it takes to eradicate a pandemic. Just think of what the modern debased US political reactions would be… It’s already almost that bad, where people refusing to mask up are assumed to be Republicans, and that widely viewed as an occasion for shame:

DoctorTitanium @ Twitter: Battle of cultural norms

Eagerly awaiting vaccination

Here at Chez Weekend, your humble Weekend Editor has gotten the first shot, and is eagerly awaiting the second. The Weekend Editrix, being a young slip of a girl, is eagerly awaiting our state guidelines lowering the age limit to her age.

So everybody wants (or should want) the vaccine.

Now, I’m not really a fan of Randy Rainbow… but once in a loooong while, his brand of silliness helps us appreciate the surreal nature of the situation. I do actually remember the song “Mr. Sandman” by the Chordettes from 1958. (Mostly because my elder siblings were listening to popular music at the time when I were nought but a wee sprout.) So… “Mr. Biden, bring my vaccine”:

Randy Rainbow @ Twitter: Mr Biden, Bring My Vaccine

Addendum 2021-Mar-14 (Pi Day!)

Boston Globe: Fauci doesn't get Republican vaccine resistance either An article in the venerable Globe by Krasny & Condon [6] interviews Tony Fauci, the now-famous head of the National Institute of Allergy and Infectious Diseases and general wizard on the subject of COVID-19 in particular. A disturbing fact:

  • 41% of Republicans would refuse any COVID-19 vaccine, and
  • 49% of Republican men would refuse, but
  • just 6% of Democratic men would refuse.

That’s… maddening! When asked about this, Fauci’s response was in line with what we found above:

“I just don’t get it,” Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases, said on NBC’s “Meet the Press” when asked about polling showing many Republicans, especially men, don’t want a vaccine.

“We’ve got to dissociate political persuasion from common sense, no-brainer public health things,” Fauci said.

Fauci also said he wished former President Donald Trump would come out and publicly urge his supporters to get the vaccine. “I wish he would,” Fauci said on “Fox News Sunday.” “It would really be a game changer if he did.”

But a decision by a large swathe of the population to not receive a vaccine may slow or imperil the march toward herd immunity in the U.S.

Yep. Right there with you, Tony. We don’t get it either. Endangering herd immunity isn’t just self-destructive, it’s dangerous for all of us. Jacobson v Massachusetts is starting to look better and better.

Notes & References

1: C Owens, “Republicans are least likely to want the coronavirus vaccine”, Axios, 2021-Feb-25.

2: D Diamond, “Meet the GOP voters who could decide whether the U.S. reaches herd immunity”, Washington Post, 2021-Mar-08.

3: L Hamel, et al., “KFF COVID-19 Vaccine Monitor: December 2020”, Kaiser Family Foundation, 2020-Dec-15.

4: A Fontanet & S Cauchemez, “COVID-19 herd immunity: where are we?”, Nature Reviews Immunology 20:10 (2020-Oct), 583–584. doi:10.1038/s41577-020-00451-5. PMC 7480627. PMID 32908300.

5: HE Randolph & LB Barreiro, “Herd Immunity: Understanding COVID-19”, Immunity 52:5 (2020-May), 737–741. doi:10.1016/j.immuni.2020.04.012. PMC 7236739. PMID 32433946.

6: R Krasny & C Condon, “Fauci says vaccine hesitancy among Republicans poses a risk: ‘I just don’t get it’”, Boston Globe, 2021-Mar-14.

Published Wed 2021-Mar-10

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