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23 Nov, 8 tweets, 3 min read
The new CDC study on mask effectiveness compares Kansas counties with and without mask mandates and finds that masks are effective.

Are they, really? (1/x)

cdc.gov/mmwr/volumes/6…
The first red flag comes from the data they used for analyses. They pick two seemingly random weeks from before and after the mandates and compare the changes in case numbers. They find that cases doubled in non-mandate counties and slightly declined in mandate counties. (2/x)
While this looks like cherry-picking, the results are actually similar when we compare mandate vs. non-mandate counties in terms of overall increase since August. On average, cases per 100K increased by x19 in non-mask counties vs. x9 in mask counties. (3/x)
This got me excited for a minute. I actually thought masks may have made a difference. Wouldn't it be wonderful if we could actually eliminate a virus by just covering our mouths for a few months? Sounds too good to be true! Because it is... (4/x)
There is a huge elephant in the room: Urban vs. rural is a giant covariate. The most populated five counties are mask counties, causing all kinds of biases in the analyses. A fair comparison would be between counties with similar populations, which is what we do next... (5/x)
For this analysis, we pick 22 (11 mask and 11 non-mask) counties. See below for which counties are included. Their populations are almost the same, with average being 30K for non-mask and 31K for mask. (6/x)
Comparing their case increases from August 11th (the date CDC report used as the cut-off) till now, we get this: Counties without mask mandates saw their cases increase x5.77, while counties with mask mandates had an 8.37x increase in cases. (7/x)
I want to clarify my position once more: I am not strongly against masks. I would love for them to work and actually save lives. I am just not seeing the evidence... (8/8)

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More from @covidtweets

23 Nov
Additional analysis on Kansas mask data: Does the size of the first wave (case levels before June) have an impact on the change in cases between August 11th - November 20th? (1/x)

Using population adjusted case numbers, below are the correlations between first wave cases, mask mandate, and change in cases after August. There is a significant negative correlation between first wave size and change after August. (2/x) Image
The correlation between masks and change is positive, meaning mandate counties had bigger changes. However, this is likely confounded by first wave size, as three counties with bigger first waves are non-mandate counties. (3/x)
Read 6 tweets
22 Nov
While it is too early for interventions to take effect in ND, I wanted to post an update regarding our quasi-experiment comparing SD/ND after ND implemented restrictions and mask mandates, effective Nov. 14th, and SD did not. (1/5)
First, cases: While ND is trending higher, both seem to have turned downward around the time ND implemented the mandates. No divergence so far. However, it is important to note that infections take around a week to be counted as a case, so any effect would not show yet. (2/5)
Second, hospitalizations: This also seems to have stabilized and turning downward in both states, although it is more pronounced in ND. (3/5)
Read 5 tweets
20 Nov
Many times, we go see a doctor or take a pill when we are feeling the worst, right before we would naturally be feeling better. Then we attribute the outcome to the intervention....

Like those who think lockdowns turned things around in Europe. (1/x)
Topol shows a few countries as examples to how "it can be done". He is missing one though, so I added that...

When these countries enacted restrictions, cases were already peaking. Lockdowns, again, did nothing. Below I show a few examples... (2/x)
UK enacted LD on Nov. 5. However, cases were flat since Oct. 24, and with a minimum 7-day delay between an infection and it being counted as a case, infections were stable since mid-Oct. Lockdowns were so effective that they worked two weeks before being implemented! (3/x)
Read 7 tweets
19 Nov
"In places where there is modest SARS-CoV-2 transmission (like Denmark during these months), there is insufficient evidence to suggest wearing a mask as you go about daily errands will protect you from infection."

Let's do a thought experiment... (1/x)
Imagine you are in combat, wearing an armored vest, which covers the areas of your body you are most likely to get shot. There are not many enemies, and a small number of bullets are coming. What are the chances that you will survive? (2/x)
But remember, if there are enough bullets, one of them will eventually hit you in the throat. Now the enemy deployed a brigade and they are raining bullets on you. What are the chances that the vest will save you? (3/x)
Read 7 tweets
18 Nov
In March, some argued that schools going remote was going to make online education more mainstream and more accepted as an effective form of instruction. I argued it was the opposite, that this was really bad for online degrees. (1/4)
Imagine being a student during all this and suffering through countless Zoom classes. Then graduating with your only online learning experience being this. Then you take on a role in which you begin making decisions about job applications. (2/4)
Then you get an application from someone with and online degree along with another a bit less qualified applicant with a traditional college degree. Which one do you give the job to? (3/4)
Read 4 tweets
18 Nov
We are currently doing what could be the closest we can get to an RCT of restrictions and mandates: North vs. South Dakota. Two very similar states, but as of last Friday, very different policies in how they approach COVID. (1/x)
On Friday, ND imposed restrictions on bars and indoor dining, indoor events, and sports. They also mandated masks. Meanwhile, SD is not changing their approach and avoiding such restrictions. Here is a look at their cases so far (source for data is CTP): (2/x) Image
Their curves are very similar, so they are starting from the same place. We will soon know if they diverge as a result of ND's interventions. However, it is important to note that they are on slightly different latitudes, so there is that. Here is hospitalizations: (3/x) Image
Read 4 tweets

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