How to vaccinate all the Germans in two easy steps

One might despair at how hopelessly behind Europe in general, and Germany in particular, is with its vaccination campaign. According to the data below from the Robert Koch Institute, they recovered last week from the collapse of the week before due to the brief rejection of the AstraZeneca vaccine, and resumed their very modest acceleration, but that seems to have stopped, and they’re now back to the rate of the previous week of about 1.5 million vaccines per week, a rate that would get them through the entire adult population in around… 2 years.

RKI Vaccine statistics 1/4/2021

But not to worry! says Der Spiegel. They quote an expert — Sebastien Dullien, scientific director of the Institute for Macroeconomics and Economic Research (Institut für Makroökonomie und Konjunkturforschung (IMK) der Hans-Böckler-Stiftung), for which I’ll have to take their word that he’s somehow an expert on vaccines and public health, because his job (and his Wikipedia page) make it seem that he’s an expert on finance and economics — who claims that the vaccination of the entire German adult population will be complete before the middle of the summer. “Es ist realistisch, alle impfbereiten erwachsenen Deutschen bis Ende Juli durchgeimpft zu haben.” [It is realistic, that we can have all willing adult Germans vaccinated by the end of July.) Sounds good! He goes on to say “Dafür müssen nur zwei Bedingungen erfüllt werden.” [This depends on just two conditions being fulfilled.] Okay, two conditions. I hope the conditions are fulfilled… What are they?

Der Impfstoff muss kommen, und er muss verimpft werden.
[We have to get the vaccine, and then we have to vaccinate people with it.]

It’s this kind of reduction of complex problems into manageable sub-problems that only the truly great minds can deliver. This goes on my list of “How-to-do-it” solutions to complex problems. (Previous entries here, here, and here.)

Actually, this is amazingly close to the Monty Python original, where the kiddie show How to Do It explained “how to rid the world of all known diseases”. Their method was more elaborate, though, involving five steps:

First of all, become a doctor, and discover a marvelous cure for something. And then, when the medical profession starts to take notice of you, you can jolly well tell them what to do and make sure they get everything right, so there will never be any diseases ever again.

Natural frequencies and individual propensities

I’ve just been reading Gerd Gigerenzer’s book Reckoning with Risk, about risk communication, mainly a plaidoyer for the use of “natural frequencies” in place of probabilities: Statements in the form “In how many cases out of 100 similar cases of X would you expect Y to happen”. He cites one study forensic psychiatry experts who were presented with a case study, and asked to estimate the likelihood of the individual being violent in the next six months. Half the subjects were asked “What is the probability that this person will commit a violent act in the next six months?” The other half were asked “How many out of 100 women like this patient would commit a violent act in the next six months?” Looking at these questions, it was obvious to me that the latter question would elicit lower estimates. Which is indeed what happened: The average response to the first question was about 0.3; the average response to the second was about 20.

What surprised me was that Gigerenzer seemed perplexed by this consistent difference in one direction (though, obviously, not by the fact that the experts were confused by the probability statement). He suggested that those answering the first question were thinking about the same patient being released multiple times, which didn’t make much sense to me.

What I think is that the experts were thinking of the individual probability as a hidden fact, not a statistical statement. Asked to estimate this unknown probability it seems natural that they would be cautious: thinking it’s somewhere between 10 and 30 percent they would not want to underestimate this individual’s probability, and so would conservatively state the upper end. This is perfectly consistent with them thinking that, averaged over 100 cases they could confidently state that about 20 would commit a violent act.