Two New Studies on Corona Mask Use: We Still Have No Idea if Masks Help

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In my town, there are huge Orwellian road signs at the hiking trailheads that read, “Wear a Mask, Save Lives!”.  I do wear my mask because they tell me to, but I also roll my eyes because the science on mask use is nowhere near that settled. Now two new studies stir that proverbial unsettled pot into a nice frothy mess. Let’s dive in.

What Type of Masks?

The masks I’m discussing here are the surgical or cloth masks that you can easily buy. We’re not reviewing whether n-95 respirators work, as the science is more convincing that those do help reduce the spread of a respiratory virus like SARS-CoV2.

The Old Science on Mask Use

The concept that wearing masks can save lives in a respiratory virus pandemic goes back decades. Hence, this is not even close to a new subject. I’ve already reviewed that research and suffice it to say that it didn’t demonstrate that mask use prevented the spread of respiratory viruses.

The Crazy Running “Study”

coronavirus exercise simulation

This one was literally some guys at a university engineering department screwing around with a computer model of how droplets would spread with runners in different positions. It never studied whether anyone could get infected because it never involved any real virus. It was also never published or even placed on a pre-print server, just released to the press. However, it did produce some seriously cool graphics that freaked out millions. Some people I observed were so frightened that they dramatically reduced their outdoor trips. That reduction in outdoor activities likely hurt more people than it helped.

Silly New Science

I have also reviewed a new population-based computer model that purported to prove that mask use saves lives (1). The problem is that the model is conjecture multiplied by more conjecture and divided by uncertainty. Basically, by slightly altering a few key variables in this mask use model, you can get it to prove that masks are bad, good, or do nothing. Hence, this study didn’t help settle the issue.

The Brand New Computer Model on Droplets

This is a study that is published, on how small water droplets can pass through cloth and surgical masks (2). It’s a computer model like the runner study above, but it’s actually been peer-reviewed, unlike that model. Here the scientists used a complex simulation of coughs and water droplets. Basically, masks helped keep small water droplets (which can carry the virus) in for the first cough. However, in repetitive coughs, the water droplets just went right around the mask. This of course is not new information, as a better study was done by NIOSH years ago that also concluded that cloth masks wouldn’t work (3).  Also, keep in mind that this is another computer model where no actual infections were measured.

The Brand New Small Town Study

This one isn’t really a peer-reviewed study as much as it is some data presented as an opinion piece in a German Labor Institute publication (4). The authors noted that the German city of Jena was the first to institute mask use and in that city, COVID-19 cases dropped by as much as 40%. You know you’re in trouble with this paper when the analytical method is described as “A Synthetic Control”. What the heck is that? A fancy way of saying that there were a slew of reasons why the COVID-19 cases may have gone down, but we used a bunch of math to convince you it was the masks. Let’s just look at a few:

  • The testing rate in Germany wasn’t constant during this time, meaning testing determines case numbers
  • Jena is a highly educated university town and home to several German research societies, so they were much more likely to comply with social distancing measures that were also imposed at the same time
  • The “control” group (no mask use) they used was “synthetic”, meaning it didn’t actually exist. So the study didn’t take one town that was identical to Jena and at the same time tell them all not to wear masks and then make sure all other variables like testing levels, social distancing metrics from cell phones, and other closures were identical.

There are also other problems called “confounders”(6). These are other things that are dramatically different about Jena that all could have impacted the COVID positive rate:

  • On March 17th, far before other German cities, Jena closed all restaurants and fitness clubs
  • On March 20th, Jena put a curfew that restricted visiting any public place other than for shopping or a physician’s visit
  • On March 24th, the mayor declared that all of Germany was a high-risk area and everyone who entered Jena had to quarantine for two weeks

This fits with what a UK scientist, Antonio Lazzarino, said in the London Times about this paper, “This is a non-experimental study, so causal inference cannot be claimed,” and “There are too many assumptions” (5).

The Public Wants Certainty

The public believes that science=certainty. However, science is really a long slog of uncertainty trying to prove certainty. Meaning that it can take decades in medicine to prove one simple issue like masks reduce the spread of COVID-19. So far, we are a VERY long way away from proving that issue. In fact, most of the careful research done before the pandemic began has shown that mask use doesn’t work. In the past few months, a bunch of far lower quality studies have been slapped together with spit and toilet paper and thrown out there or rushed through journals just to get something published. Regrettably, the quality of this new research is poor, which gets us no closer to definitively answering this question.

The upshot? The science on this issue of mask use is far from settled! Hence, I give you permission to roll your eyes when you see Orwellian signs in your community. In the meantime, I’ll continue to wear a mask where they tell me I should and know that nobody really has any solid idea whether my mask, or anyone else’s mask, is helping anyone.



(1) Imperial College of London. Report 9: Impact of non-pharmaceutical interventions (NPIs) to
reduce COVID-19 mortality and healthcare demand. Accessed 5/29/20.

(2) Dbouka T, Drikakisb D. On respiratory droplets and face masks. Physics of Fluids. Volume 32, Issue 6. DOI: 10.1063/5.0015044

(3) Rengasamy S, Eimer B, Shaffer RE. Simple respiratory protection—evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. Ann Occup Hyg 2010 Jun 28;54(7):789-98

(4) IZA Institute of Labor Economics. Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach. IZA DP No. 13319, June 2020

(5) The London Times. Facemasks slow spread of coronavirus by 40 per cent, study shows. Accessed 6/19/20.

(6) Zeit Online. Warum Jena? Accessed 6/25/20.

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18 thoughts on “Two New Studies on Corona Mask Use: We Still Have No Idea if Masks Help

  1. Sam

    AS for Germany, according to the Leaked Report of Germany’s Ministry of Interior drafted by a scientific panel of medical experts from several German universities:

    The disease COVID-19 triggered by the coronavirus SARS-CoV-2 is serious for many people in the known risk groups. As with any serious infectious disease, it is important to find the best treatment for the patient and prevent infection routes. But THERAPEUTIC AND PREVENTIVE MEASURES MUST NEVER BE MORE HARMFUL THAN THE DISEASE ITSELF. The aim must be to protect the risk groups without endangering medical care and the health of the general population, AS IS UNFORTUNATELY THE CASE RIGHT NOW. We in science and practice as well as many colleagues experience the consequential damage of the corona protective measures to our patients every day.

    The dangerousness of Covid-19 was overestimated: probably at no point did the danger posed by the new virus go beyond the normal level. The people who die from Corona are essentially those who would statistically die this year, because they have reached the end of their lives and their weakened bodies can no longer cope with any random everyday stress (including the approximately 150 viruses currently in circulation). There is no evidence that this was more than a false alarm. More people are dying because of state-imposed Corona-measures than they are being killed by the virus.

  2. Marc S Cahn

    On the other hand there really is not a lot of downside to wearing one as long as you don’t have severe respiratory issues. And just perhaps they work a little bit to reduce the infectious rate. No harm no foul.

  3. Terrence

    Wifey and I just had Sunday breakfast at Goodfellas. Seemed like only the servers wore masks, some hanging on the chin, and some below the nose. The restaurant is a noisy, happy Italian place with loud conversation and mix’s of young and old… good plain ample food. We wore our masks… cloth… and I noticed my beloved’s when upon the nose was pretty loose, and mine a little better. So, the function of the mask obviously is social, more than functional. I decided the main value of masks is to remind folks there is a contagious disease afoot, so if there is a sneezer or coughed in their vicinity they can pull the mask on tighter, hope, and maybe move away a little. Most folks are not technical, and just comply with the moti9ns, I believe, and not the details.
    Nice to read the Centeno introduction of the truth, which dispels all the hype, but helps, a really. Gratias.

  4. Nancy Thorne

    Chris, I spent twelve thousand dollars at your clinic (San Rafael) in 2016.
    So, are you a Trumpanzee??
    Politics over science….sad!!

    1. Chris Centeno, MD Post author

      Nancy, I cover science, not politics. I just put this to a vote and about 95% of the readers stated more hard-hitting COVID articles covering the science.

  5. Jill

    My question is – why do you act in a manner contrary to your own belief about masks just because someone tells you to? I feel no obligation to wear a mask so someone else can “feel safe”. I have no control over how someone else feels. And I certainly don’t wear a mask just because someone tells me to when I don’t believe there is good evidence to support its effectiveness. I also don’t always drive the speed limit.

    1. Chris Centeno, MD Post author

      I personally have no issue with wearing a mask if it makes someone else feel comfortable. I also don’t have any issue with those that chose to exercise their right not to wear one.

  6. Joe Hong

    It seems that Dr. Centeno is not being as crystal clear as he usually is in this blog. There should be no disagreement among experts that wearing a cloth mask does not protect the person wearing the mask. This particular point is over and done with and there is no need to revisit if only to confuse the next point.
    At the same time, there is an abundance of evidence that if the person who is wearing a cloth mask is pre-symptomatic or asymptomatic, the fact that he is wearing the mask help minimize transmission to everyone else. Even the Lancet study reviewed and cited by Dr. Centeno is very clear on this point.
    I don’t like wearing a mask myself. But wearing it is not for me, it is for everyone else just in case I become infected and not know it. So I wear the mask in public.

    1. Chris Centeno, MD Post author

      Joe, you don’t get to claim that you wearing a cloth mask helps someone else on this blog without a significant number of scientific citations that directly measured SARS-CoV2 transmission in a randomized manner. Given that I have now reviewed this literature several times in the past few months, you won’t be able to find those citations, hence your claim that we have proof that we are wearing masks to protect others is false right now.

  7. Wolfgang

    I live in Jena. Even before the first Corona case, the mayor of Jena issued a general ruling on March 11th. This concerned the obligatory quarantine for travel returnees from all risk areas, which prevented an explosion of case numbers in Jena. Before the introduction of the compulsory mask, Jena had 122 cases of infection. Currently there are 161.
    Entry controls and quarantine are the most important measures! Masks do no harm.
    Translated with (free version)

    1. Chris Centeno, MD Post author

      Thanks for the info. Hence, there were already aggressive controls in PLACE that were atypical BEFORE make use was mandated. That’s what’s called a “co0nfounder”!

  8. David Smith

    This is an engineering issue first, not a medical issue. It’s a matter of pressure drop, which for a mask is too high to be a filter so most of the air passes around the mask and not through it. At best it is a splatter shield. Unless you are leaning right over someone or them you, there is little to no benefit. The trajectory of any droplet that it may catch is just too short to be a legitimate health risk short of the “sardine” factor. Then there is particle size of what you are trying to filter, which is so small that to be effective, drives up the pressure drop so much, that the surface area of the mask would have to be gigantic to filter at breathing pressures.
    This is nothing other than a fear and guilt device. Wear it by choice and your comfort but don’t shame others for living life freely with logic and reason.

  9. Jill

    Amen, David Smith! Masks are probably useful to prevent a surgeon from drooling into your open wound on the surgery table. Other than that, they’re virtually useless unless you have been manipulated into believing you have a liability risk without one. The more focus that is put on containing any rogue germ that might escape, the more terrified people become and thereby the more easily manipulated. As for the harmlessness of wearing a mask, I’m not so sure. I think a case could easily be made for mask wearing actually compromising the wearer’s immune system.

  10. Rondo

    What do you make of this experiment regarding masks?

    1. Chris Centeno, MD Post author

      The problem is that surgical masks were designed to prevent bacterial and not viral spread. In addition, he didn’t measure the stuff that just goes around the mask.

  11. Rondo

    Thanks, you guys are great, I’m learning so much

  12. rondo

    This is the response I got sending this article to a blogger

    “Nonsense. The same people who claim that you shouldn’t wear masks support the anti-vaxxers.

    The overwhelming majority of the research supports wearing masks. Cuts spread by 85-95%.”

    1. Chris Centeno, MD Post author

      I’m a physician who is not anti-vaccine. So the next step is to ask to see his review of the scientific literature showing that masks reduce the spread of the SARS-CoV2 virus. Specifically, randomized controlled trials which show that mask use reduces the spread of respiratory viruses.

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