One thing that you didn’t account for—the method of directly scaling the Rt by the multiple on the R0 (which seems to be around 1.55), is only a rough estimate of how much the Rt will increase by when the effective Rt is lowered in a particular situation. It could be almost arbitrarily wrong—intuitively, if the hairdressers are closed, that prevents 100% of transmission in hairdressers no matter how much higher the R0 of the virus is.
For this reason, the actual epidemiological models (there aren’t any for the US for the new variant, only some for the UK), have some more complicated way of predicting the effect of control measures. This from Imperial College:
We quantified the transmission advantage of the VOC relative to non-VOC lineages in twoways: as an additive increase in R that ranged between 0.4 and 0.7, and alternatively as amultiplicative increase in R that ranged between a 50% and 75% advantage. We were not ableto distinguish between these two approaches in goodness-of-fit, and either is plausiblemechanistically. A multiplicative transmission advantage would be expected if transmissibilityhad increased in all settings and individuals, while an additive advantage might reflect increasesin transmissibility in specific subpopulations or contexts.
The multiplicative ‘increased transmissibility’ estimate will therefore tend to underestimate the effect of control measures. The actual paper did some complicated Bayesian regression to try and figure out which model of Rt change worked best, and couldn’t figure it out.
Measures like ventilation, physical distancing when you do decide to meet up, and mask use will be more multiplicative in how the new variant diminishes their effect. The parts of the behaviour response that involve people just not deciding to meet up or do things in the first place, and anything involving mandatory closures of schools, bars etc. will be less multiplicative.
I believe this is borne out in the early data. Lockdown 1 in the UK took Rt down to 0.6. The naive ‘multiplicative’ estimate would say that’s sufficient for the new variant, Rt=0.93. The second lockdown took Rt down to 0.8, which would be totally insufficient. You’d need Rt for the old variant of covid down to 0.64 on the naive multiplicative estimate—almost what was achieved in March. I have a hard time believing it was anywhere near that low in the Tier 4 regions around Christmas.
But the data that’s come in so far seems to indicate that Tier 4 + Schools closed has either levelled off or caused slow declines in infections in those regions where they were applied.
First, the random infection survey—London and South East are in decline and East of England has levelled off (page 3). The UKs symptom study, which uses a totally different methodology, confirms some levelling off and declines in those regions—page 6. It’s early days, but clearly Rt is very near 1, and likely below 1 in London. The Financial Times cottoned on to this a few days late but no-one else seems to have noticed.
I think this indicates a bunch of things—mainly that infections caused by the new variant can and will be stabilized or even reduced by lockdown measures which people are willing to obey. It’s not impossible if it’s already happening.
To start, let’s also ignore phase shifts like overloading hospitals, and ignore fatigue on the hopes that vaccines coming soon will cancel it out, although there’s an argument that in practice some people do the opposite.
I agree with ignoring fatigue, but ignoring phase shifts? If it were me I’d model the entire control system response as a phase shift with the level for the switch in reactions set near the hospital overwhelm level—at least on the policy side, there seems to be an abrupt reaction specifically to the hospital overloading question. The British government pushed the panic button a few days ago in response to that and called a full national lockdown. I’d say the dominant contributor to control systems is something like a step function at a particular level near where hospitals are overwhelmed, and individual responses proportionate to exact levels of infection are a lesser part of it.
I think the model of the control system as a continuous response is wrong, and a phased all-or-nothing response for the government side of things, plus taking into account non-multiplicative effects on the Rt, would produce overall very different results—namely that a colossal overshoot of herd immunity in a mere few weeks is probably not happening. I note—outside view—that this is very similar to the predictive mistake made last Febuary/March with old Covid-19 - many around here were practically certain we were bound for an immediate (in a month or two) enormous herd immunity overshoot.
So you’re saying that you think that a more infectious virus will not increase infections by as high a percentage of otherwise expected infections under conditions with more precautions, versus conditions with less precautions? What’s the physical mechanism there? I don’t understand it, and if I’m going to believe it, I’ll need an explanation of physically how it works that way, if it works that way.
As for the outside view thing, well, sure, of course, but it doesn’t sound like you have very different models of what might be done by people in these scenarios this time—your theory is that the lockdowns can work.
But I’d also ask, even if it would be enough, how long do you think England is prepared to keep the Tier 4 + Schools thing in place for and get cooperation? And do you think the USA could get to that level at all at this point? Especially given it only levels things off at a very high level, and doesn’t actually make much progress, so you can never relax. And the overall UK numbers are still steadily getting worse.
So you’re saying that you think that a more infectious virus will not increase infections by as high a percentage of otherwise expected infections under conditions with more precautions, versus conditions with less precautions? What’s the physical mechanism there?
Wouldn’t “the fractal nature of risk taking” cause this? If some people are taking lots of risk, but they comply with actually strict lockdowns, then those lockdowns would work better than might otherwise be expected. No?
But I’d also ask, even if it would be enough, how long do you think England is prepared to keep the Tier 4 + Schools thing in place for and get cooperation? And do you think the USA could get to that level at all at this point? Especially given it only levels things off at a very high level, and doesn’t actually make much progress, so you can never relax. And the overall UK numbers are still steadily getting worse.
One thing that you didn’t account for—the method of directly scaling the Rt by the multiple on the R0 (which seems to be around 1.55), is only a rough estimate of how much the Rt will increase by when the effective Rt is lowered in a particular situation. It could be almost arbitrarily wrong—intuitively, if the hairdressers are closed, that prevents 100% of transmission in hairdressers no matter how much higher the R0 of the virus is.
For this reason, the actual epidemiological models (there aren’t any for the US for the new variant, only some for the UK), have some more complicated way of predicting the effect of control measures. This from Imperial College:
The multiplicative ‘increased transmissibility’ estimate will therefore tend to underestimate the effect of control measures. The actual paper did some complicated Bayesian regression to try and figure out which model of Rt change worked best, and couldn’t figure it out.
Measures like ventilation, physical distancing when you do decide to meet up, and mask use will be more multiplicative in how the new variant diminishes their effect. The parts of the behaviour response that involve people just not deciding to meet up or do things in the first place, and anything involving mandatory closures of schools, bars etc. will be less multiplicative.
I believe this is borne out in the early data. Lockdown 1 in the UK took Rt down to 0.6. The naive ‘multiplicative’ estimate would say that’s sufficient for the new variant, Rt=0.93. The second lockdown took Rt down to 0.8, which would be totally insufficient. You’d need Rt for the old variant of covid down to 0.64 on the naive multiplicative estimate—almost what was achieved in March. I have a hard time believing it was anywhere near that low in the Tier 4 regions around Christmas.
But the data that’s come in so far seems to indicate that Tier 4 + Schools closed has either levelled off or caused slow declines in infections in those regions where they were applied.
First, the random infection survey—London and South East are in decline and East of England has levelled off (page 3). The UKs symptom study, which uses a totally different methodology, confirms some levelling off and declines in those regions—page 6. It’s early days, but clearly Rt is very near 1, and likely below 1 in London. The Financial Times cottoned on to this a few days late but no-one else seems to have noticed.
I think this indicates a bunch of things—mainly that infections caused by the new variant can and will be stabilized or even reduced by lockdown measures which people are willing to obey. It’s not impossible if it’s already happening.
I agree with ignoring fatigue, but ignoring phase shifts? If it were me I’d model the entire control system response as a phase shift with the level for the switch in reactions set near the hospital overwhelm level—at least on the policy side, there seems to be an abrupt reaction specifically to the hospital overloading question. The British government pushed the panic button a few days ago in response to that and called a full national lockdown. I’d say the dominant contributor to control systems is something like a step function at a particular level near where hospitals are overwhelmed, and individual responses proportionate to exact levels of infection are a lesser part of it.
I think the model of the control system as a continuous response is wrong, and a phased all-or-nothing response for the government side of things, plus taking into account non-multiplicative effects on the Rt, would produce overall very different results—namely that a colossal overshoot of herd immunity in a mere few weeks is probably not happening. I note—outside view—that this is very similar to the predictive mistake made last Febuary/March with old Covid-19 - many around here were practically certain we were bound for an immediate (in a month or two) enormous herd immunity overshoot.
So you’re saying that you think that a more infectious virus will not increase infections by as high a percentage of otherwise expected infections under conditions with more precautions, versus conditions with less precautions? What’s the physical mechanism there? I don’t understand it, and if I’m going to believe it, I’ll need an explanation of physically how it works that way, if it works that way.
As for the outside view thing, well, sure, of course, but it doesn’t sound like you have very different models of what might be done by people in these scenarios this time—your theory is that the lockdowns can work.
But I’d also ask, even if it would be enough, how long do you think England is prepared to keep the Tier 4 + Schools thing in place for and get cooperation? And do you think the USA could get to that level at all at this point? Especially given it only levels things off at a very high level, and doesn’t actually make much progress, so you can never relax. And the overall UK numbers are still steadily getting worse.
Wouldn’t “the fractal nature of risk taking” cause this? If some people are taking lots of risk, but they comply with actually strict lockdowns, then those lockdowns would work better than might otherwise be expected. No?
Hi I am a political scientist and I have an article about this exact question. You can read it here and give constructive comments—https://www.lesswrong.com/posts/em5HYZ6cq9tt65842/why-lockdowns-failed-a-letter-to-the-policy-entrepreneurs-in