08 July 2021

Lagging indicators

 Vaccine effectiveness is measured; you give the vaccine to a number of people, and you count how many of them get sick from the thing you vaccinated them against, and you compare that to the expected number of sick people without vaccination.

The ethics panel won't let you deliberately infect your test group to see who gets sick from exactly how much measured exposure.  You're stuck using random exposure, and that is affected by behaviour.

We've known almost from the beginning that COVID-19 is a dose-dependent disease; how sick you get is influenced by how much virus you were exposed to when you were infected.

People who are not sure if they got the vaccine or the placebo, and who are further not sure that the vaccine works, go right on being cautious.  Caution reduces both their chance of being exposed and their dose if they are exposed.  (They are, after all, the sort of pro-science public-spirited people who sign up for vaccine trials; they don't want to get sick and they're at least aware of the "how not to get sick" guidelines and are probably following a bunch of them.)

People who think they're now immune are less cautious.  They get exposed more often and to statistically larger doses.  They get sick more than the test group does; the measured vaccine effectiveness is observed to go down.

Sure as death, the vaccine effectiveness has been reduced; that's exactly what you expect selection to do when you've got a functional vaccine, a big population of variously infected and vaccinated people, and long illnesses which give the virus a sustained period of reproduction in which to mutate.  But we can't tell how much is selection, and how much is a change in behaviour, without doing experiments to which that ethics board would rightly object.

In terms of things you can change, vaccine effectiveness is a lagging indicator of behaviour.  The vaccine you received is more effective if you distance, mask, and avoid going inside anywhere but your home like the plague.  If you act like COVID-19 doesn't exist, the vaccine is less effective.

(The medical statisticians trying to pull apart how much is behaviour and how much is virus variation have an unenviable job.  We'll never know without significant error bars.  But for planning purposes, here at individual scale, vaccine effectiveness is a lagging indicator of behaviour.)


JReynolds said...

Here's hoping that the numbers in Ontario continue their downward trend after the 14th.

Canada should* ban travel from the UK pretty soon though. Who would have thought having a bunch of incompetent mammonites in charge would have such negative consequences?

*But probably won't, until it's too late.

Graydon said...

I suspect there's a combination of "they can't be serious" (about the Johnson government's stated policies) and institutional difficult with banning travel from Mother England.

Mammonism is about money; people aren't even grease in the gears. The fate of anybody whose traditional land happened to sit over desirable minerals should have made it obvious just how well a mammonite system would do with a plague, but the emotional connection never seems to be obvious.

Anonymous said...

Challenge trials really is the only way. Hopefully the UK is a good example here

Graydon said...


Challenge trails against what? SARS-CoV-2 is evolving faster than you could plausibly test.

One of the really difficult things, culturally, is that there's no solution to the Uncommon Cold that permits a return to the status quo ante pestis.

(Same with the Carbon Binge, and the time of angry weather; there is no way to keep the status quo.)

This is not necessarily bad; there are a lot of indicators (influenza, asthma) that less exposure to viruses is a net win for many people in many respects. And the overall benefit to individuals of ceasing to do a mammonism is large. It's just something the folks with the great concentrations of money and thus agency are willing to kill us all to avoid.

Moz said...

Oooh, you fancy northerners with your widespread vaccine availability think you're so special. "does it still work when the vaccinated population change their behaviour" is such an elite question. Down here in the special country we're still "negotiating" for supplies of vaccines and arguing about whether private school boys deserve the vaccine more than nurses do.

I'm in NSW and the state government was finally forced to upgrade their "voluntary stay at home suggestion" a lockdown once it became obvious that the suggestion was almost useless. The actual lockdown is still quite shit because they refuse to define what an "essential business" is (so fashion shops are open) or police even the most egregious violations of the rules.

Meanwhile thousands of people in Australia are fully vaccinated. Thousands!

Moz said...

One of the exciting changes has been working from home. Sure, it's mostly something the already affluent are able to do, but at the same time they tend to be the largest polluters so that change will have a disproportionate benefit.

As someone who is in that group and deeply pissed off at the behaviour of my peers on a whole raft of issues, I am quite thrilled that not only can "we" not drive to work every day, but "we" also can't fly off around the world on a whim any more. The limited stats I've seen say that the increase in buying stuff online does not come anywhere near compensating for the lack of transport emissions.

This suggestion is also amusingly audacious: https://norightturn.blogspot.com/2021/07/free-e-bikes-for-all.html

(I just bought a heavily used and badly maintained ebike and am fixing it up. It's fun to ride and definitely makes load carrying easier. Hopefully the friend I bought it for will actually use it...)

JReynolds said...

An interesting bit I heard on the CBC this morning (2021-07-13): one Ontario doctor says that Ontario is in a fourth wave right now. However, since this one is targeting the unvaccinated, it's hardly making a blip in the daily COVID numbers.

Pity it's not just ignorant gits dealing with this, but kids and those who can't (for legitimate reasons) get the vaccine.