We can be very grateful for the North Dakota experiment of mandating masks and social distinacing to show the potential effect of controlling transmission.
Naievly, it seems that cases appear to decline more rapidly in North Dakota compared to South Dakota shortly after the mandate which occurred right at the peak of cases.
However, simply stripping out the effect of differences in testing rates, it is apparent that cases drop slightly more quickly in North Dakota because they rose slightly more quickly since 26-Oct before both States settle back into lockstep in mid-Dec.
On the basis of this simple experiment, there does not seem to be any apparent benefit on COVID transmission due to combined measures of community mask-wearing and social distancing in businesses.

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More from @RealJoelSmalley

24 Feb
Grateful to a colleague who pointed out that North Dakota quietly lifted their restrictions on 18-Jan, I'm reposting my analysis of the Dakotas, two US states that are almost identical in geographic and demographic terms. ImageImage
The Sturgis bike rally was blamed for starting the widespread transmission. Although it is clearly a superspreader event, it is not the cause for the start of transmission nor the continued spread. Masks and social distancing show no obvious benefit when introduced only in ND. Image
Curiously, transmission resurgence over the festive period (another superspreader event?) seems to be worse in ND than SD while the mandates remain in force. There is no apparent rebound whatsoever when interventions are lifted on 18-Jan. Image
Read 9 tweets
23 Feb
I guess everyone has heard about the "spectacular" results of the vaccine in Scotland? bbc.co.uk/news/health-56… Much like The Telegraph/Spiegelhalter "conclusions" last week, I'm sorry, but I have a real problem with the maths... So much so that I couldn't sleep last night...
The success seems based on the premise that deaths have fallen much faster in the oldest age group post vaccination compared to other age groups. But just like the English "analysis", there doesn't seem to be any mention of what deaths were doing before vaccination started?
The Scottish data isn't very good or accessible but the pattern is still pretty clear. Before vaccinations started, deaths across all age cohorts were decreasing. They all increase on 29-Dec.
Read 8 tweets
15 Feb
I'm not sure how to explain this in layman terms so here is an analogy to explain what I see in the growth rate of cumulative COVID deaths for 75+ year olds. Imagine a car coasting. In spring, the car is always slowing down, until eventually it stops.
In winter, it's like it's costing from 20-Dec and then the driver touches the accelerator on 01-Jan. After that you can clearly see that the rate of growth is decreasing linearly, not exponentially as witnessed everywhere I've modelled in spring and autumn.
Here it is zoomed in. In spring, the deceleration is slower than expected as a function of how it started out but still clearly exponentially decreasing all the same.
Read 4 tweets
15 Feb
Interesting little analysis on COVID deaths by age...

This has promted me to dig deeper. I find the outperformance in the 20-64s starts some time between 12-Dec and 19-Dec. The peak in rate of growth is between 05-Jan and 12-Jan.
The 85+ rate of growth accelerates from 02-Jan and peaks definitvely on 11-Jan. Since mid-Jan, there is no discernible difference in the rate of growth between that cohort and the 85+.
Read 5 tweets
14 Feb
NYC is a good analaysis candidate. Clearly a homogeneous geography so the virus spreads very closely to model expectations with interventions coming too late to have much impact at all. Very densely populated, the epidemic lasts 13 weeks unfettered with 20k deaths.
In Autumn, a smaller, residual wave appears with very similar characteristics to Spring, 16 weeks long, 1,100 deaths.
But then in mid-Dec, starting almost at the peak of that wave, another one emerges. This is most unusual, starting in the middle of another wave in such a homogeneous region. Furthermore, it has both a higher attack rate and longer expected duration. Counter-intuitive.
Read 6 tweets
13 Feb
I am looking again at the rest of Europe, starting with Portugal. Exactly the same picture as England. I estimate net 1,400 deaths postponed in Spring but it would have been over in 19 weeks with 3,200 deaths with no interventions.
In Autumn/Winter, with better conditions, the virsu would have accounted for 6,000 deaths, again within 20 weeks with no intervention. However, what appears since Xmas is not the same. The process implies a 43 week duration. This is not naturally self-limiting.
France did not have quite the same success with interventions as Portugal in Spring, postponing about 23% of deaths. With no intervention the epidemic would have lasted 15 weeks, accounting for 39,000 deaths instead of 30,000.
Read 4 tweets

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