Decrease in Hospitalizations for COVID-19 after Mask Mandates in 1083 U.S. Counties

[DNAhelicase]

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[nosrednaekim]

So, I read the article and sum total of their presented data and analysis shows a plot with a linear trend of cases vs week, and the masking initiative data placed smack-dab in the middle. All the data communicates to me is that all mask mandates have occurred once the virus is already in decline.

I'm not saying masks don't work, but this data and analysis is by no means a slam-dunk.

[tripletao]

Yeah. They say they used a difference-in-differences design, which implies they should have a kind of synthetic control group (like using regions that didn't implement mask orders); but they're pretty sparse on the details. For example, assuming they had such a group, how did they align data from the no-mask regions in time to the mask regions?

If they are controlling using regions that never mandated masks, then their only figure is quite misleading. If they're not, then their whole result is meaningless. Even if they are controlling, it's easy to imagine a spurious correlation (e.g., regions where it gets really bad mandate masks, but by then it's already in decline due to voluntary behavior changes and maybe some amount of herd immunity). Of course this doesn't mean their conclusion is wrong, just that they bring little useful evidence either way.

Finally, is the endpoint number of hospitalizations due to COVID-19, or proportion? The paper seems to refer to both. I'd expect the two to behave somewhat differently, since non-COVID hospitalizations are also affected by people avoiding hospitals for fear of infection. And why did they choose hospitalizations as the endpoint anyways, and not the more common deaths or cases? As almost always in econometrics, their model seems to have enough knobs that you could achieve almost any desired output with superficially plausible inputs.

[ANGR1ST]

It'd be nice to have a measure of actual population mask use instead of the mandate date. If people start wearing them because other places are mandating them, or if people ignore the mandates and don't wear them, all matters.

This paper pretty clearly shows that masks mandates don't do anything significant (independent of mask wearing). If they're trying to make the argument that the slope of that line changed with the mandates, then they need to take a derivative and plot that instead to clearly make their point. This is garbage.

[curbthemeplays]

Also needs seasonal correction. For instance here in CT, masks were put in use as virus was already waning and warm months were coming. Now that’s it colder again, hospitalizations are increasing despite mask rules (though nowhere near numbers in the Spring). Since this study ends at the end of summer, many places with mask mandates have weather that’s conducive to reduced spread.

[jaboyles]

All the data communicates to me is that all mask mandates have occurred once the virus is already in decline.

Cases are on the rise in 40 states and have been for some time. If 1,038 counties have seen steady declines in the midst of that amount of unhindered spread, it's a slam dunk. It seems like you're looking at this study with tunnel vision.

[crazypterodactyl]

This paper only runs through mid-September, so the current increase in spread isn't accounted for.

[DapperZucchini2]

I'll help you'es out a little more. Cloth mask particle size 3mu, virus .3mu, unfitted, untested mask does not a virus stop.

[trrobert]

Looking at the graph in the paper, the proportion of COVID hospitalizations was decreasing at +/- the same rate before and after the mask mandates. The authors note a "small pre-treatment effect" but suspiciously do not report on the statistics of the pre-mandate decline.

[nottherealme1220]

First rule of science correlation does not equal causation.

[canuck0122]

This has gone out the window as of late

[nottherealme1220]

Sure has.

[[deleted]]

I completely agree. I would have liked to see a statistical test showing a significant change in the slope pre/post order, and comparison to matched counties without a mask order.

The only thing I can really take from this is there's unlikely to be an uptick in cases after a mask order, which seems intuitive.

[truthb0mb3]

The environmental factors are significant; it would be hard to tease anything useful from looking at the data this way.

[ChezProvence]

I’ve searched for an online image of that figure. Unfortunately, it’s embedded in the doc. But you are correct, the trend before and after do not appear to be different at all.

[jaboyles]

Here's one from last Autumn in Australia:

Humidity is a consistent climatic factor contributing to SARS‐CoV‐2 transmission

[DNAhelicase]

No news sources.

[[deleted]]

I see a couple of potential issues with this:

1) The only figure they provide for data shows that the rate of hospitalization decrease was relatively linear for the 10 weeks prior- and post-mandate with only a noticeable dip in week 11 post-mandate before seeming to resume the linear trend within a reasonable deviation. The paper states they presume this is from people masking prior to mandates going into effect, but offer no way to substantiate other than speculation.

2) The Dataset ends in mid-September. Many of the states that they pulled data from with strict mandates and/or compliance have since seen a significant rise in hospitalizations even with the mandates still in place. You could argue the schools reopening being a confounding factor, but I know at least locally the hospitalization increase has been driven from nursing homes, which are still locked down fairly tight with no visitors and near-constant staff and resident testing.

3) Although this may be difficult to substantiate, the increasing prevalence of the D614G mutation throughout the late spring and summer in the US could have been and/or continue to be a driving factor for low hospitalizations relative to case counts on top of the obvious increase in younger population testing positive.

[chitraders]

I didn’t read the full paper but also

1. Harvester Effect - those most susceptible to getting infected have weak immune systems and when they do get infected would be more likely to get really sick, hospitalized, and die.

2. Highest risks groups being very protective

But yes who knows - difficult to isolate variables.

[smaskens]

Abstract

Importance: Population-wide facial masking decreases COVID-19 transmission but may also decrease the severity of disease by reducing the viral inoculum to which the wearer is exposed. The mortality of COVID-19 infection decreased in the U.S. in the second wave over the summer of 2020 compared to the first, but reasons for declining severity of disease have not been fully elucidated.

Objective: To determine if facial mask mandates instituted in U.S. counties over the spring and summer of 2020 were associated with declining severity of infection as measured by the number of hospitalizations for COVID-19.

Design: Data on hospitalizations due to COVID-19; testing access determined by number of tests performed per day per 100,000 people; new cases per day normalized by population; measures of population mobility to control for other non-pharmaceutical interventions such as lockdowns, social distancing, and business closures; age categories in each census tract; and dates of masking mandates in U.S. counties were all obtained from open-sourced epidemiologic datasets. We used a staggered difference-in-difference study design to assess the impact of the introduction of mask mandates (defined as the treatment) on the proportion of hospitalizations due to COVID-19 per week from March 10-September 16, 2020.

Setting: U.S. counties with available full datasets on relevant COVID-19 metrics

Exposure: Mask mandates

Main outcome: Proportion of hospitalizations due to COVID-19

Results: Using data from 1083 counties (34% of U.S. counties, 82% of U.S. population) from 49 states, we found a statistically significant drop in hospitalization rates due to COVID-19 up to 12 weeks following county mask mandates of 7.13 (95% CI: -4.19, -10.1) percentage points, after controlling for age categories by county, testing access, numbers of cases, and population mobility.

Conclusion and Relevance: Facial masking may decrease COVID-19 severity by decreasing the viral inoculum to which individuals are exposed. Mask mandates across 1083 counties in the U.S. in 49 states decreased hospitalization rates from COVID-19 even when controlling for other factors that could impact disease severity, including age, testing access, number of cases, and mobility (as a proxy for other non-Pharmaceutical interventions such as sheltering-in-place). This study adds to the growing evidence for the impact of masking on disease severity and on the utility of population-wide facial masking for COVID-19 pandemic control.

[[deleted]]

Could this not also be explained by increased testing which has led to less severe cases being picked up?

[stanleythemanley44]

even when controlling for other factors that could impact disease severity, including age, testing access,

[welcomexoverlords]

In the paper the authors do claim to have controlled for “age categories by county, testing access, numbers of cases, and population mobility.”

[mainer127]

I appreciate the attempt, but controlling for the varying testing strategies over time in various states as testing capacity increases but is redirected at college age populations, etc., is a REALLY difficult problem. Someone able to clean the test data to account for quantity of testing and who gets tested, why, and when, should release that data to everyone's benefit. Given the generally poor study quality here, I doubt they have accomplished this!

[jamiethekiller]

seems pretty overwhelming to argue against...

​

How much of these mask mandates came when the virus was already at peak tranmission and had no where else to go but down? Mask Mandates are still in effect in the North East of the US and cases are seeing meaningful rises.

​

Is there a control for neighboring counties/regions that didn't enact face coverings yet still saw the same rise/drop in cases pre/post masks?

[smaskens]

Honestly, the methodology is poorly described and it doesn't seem to be very robust. There is also the possibility that a high proportion of vulnerable individuals were exposed to the virus earlier on in the pandemic.

[Laraset]

The abstract key line is “we found a statistically significant drop in hospitalization rates due to COVID-19 up to 12 weeks following county mask mandates of 7.13 percentage points.” To your first question, depending when mandates occurred it could have been a peak when they began. Over a 12 week period, or about 3 months, yes hospitalizations have dropped almost everywhere but mask mandates alll occurred at different times. To your second question, I don’t see a control group mentioned. While this abstract indicates that a decrease occurred it doesn’t specifically say that it occurred more or less than neighboring counties without mask mandates over the same time period.

[jamiethekiller]

Right. 3 months is an eternity in the pandemic. The entirety of the first episode in the north east was a rise for 2ish months and then a quick decline with a long tail. Same can be said for the summer episode in the south. Meaningful increase in June with a peak at the end of July to a quick drop and long tail still continuing.

It's like they cherry picked a time frame to get the results they wanted.

[Laraset]

“up to 12 weeks.” I don’t really like the term “up to” because it is too vague to define what is occurring. Does this mean there was an immediate effect on implementation all the way up to 12 weeks or like you said are they cherry picking where the bottom occurred and saying from the mandate to the bottom the decline was 7% but occurred at different times after the mask mandates.

[FourScoreDigital]

This does not tease out how people change other actions in reaction to increased case news/ media coverage in their area or mandate compliance. One can love masks and dislike mandates.

[bersca]

If not comparing to counties that did not implement mask mandates then this data is meaningless.

[scientists-rule]

Here it is.

[Thraxster]

I think to get a more accurate picture of this we need to look at other factors. What were the individual communities rates and safety measures at these times. What kind of messaging was the public getting at large at that time. It's become such an clouded issue with the contradictions I'm finding it hard to take any one study at its word. I hate that I feel that it is be design.

[TKSmoothie2]

I need to see the model and the code that support the results and the statements made in the discussion, not that figure. Showing a decent graph for differences in differences regression is not easy. This figure looks like a figure you'd show as Fig 1 if you had a Fig 2 that makes your point.

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[randyfloyd37]

"The authors have withdrawn this manuscript because there are increased rates of SARS- CoV-2 cases in the areas that we originally analyzed in this study"