The Science of Masks 10: A Century of Masks
Finally, the end. Or is it? We never seem to learn.
I’ve now completed season 1 of Dharma & Greg, and you will soon have completed this overly obsessive series of blog posts. So launch Spotify and put on Revolution by Uppermost, and let’s drive this coffee table to Idaho.
That last sentence made exactly as much sense as mask mandates.
100 years, still no answers
The discussion about the ability of masks to prevent infection in the general populace is already a century old. Here’s a delightful paper from 1920, before all the ladies decided that masks didn’t go with beaded flapper dresses and quite sensibly refused to wear them (the masks, not the dresses).
1. An Experimental Study of the Efficacy of Gauze Face Masks (Kellogg & MacMillan 19201)
In 1920, W. H. Kellogg, M.D. and Miss Grace MacMillan, Bacteriologist, published the results of their experiments with gauze masks following the 1918 influenza epidemic.
[“Miss Grace MacMillan, Bacteriologist” is something you will never see in the title of a paper published in the 21st century, and that’s a shame.]
This investigation is scientific in character, omitting no one of the necessary factors. It ought to settle the much argued question of masks for the public.
The authors conducted the study because the country had just experienced a deadly epidemic - in this case of influenza. During the epidemic mask wearing was made mandatory in some cities and towns in California, but without clear evidence this would provide any benefit.
The recent epidemic of influenza brought forcibly to attention the use of the gauze mask as a protection against infection.
Their experiments were mechanistic in nature, like the studies referenced by the CDC (look how far we’ve come!) These experiments showed that masks can, in theory, limit the amount of pathogens inhaled by the wearer. Note this is before the discovery of the influenza virus* so the authors were looking at bacterial transmission in their experiments.
*[The human influenza virus was not isolated until 19332]
Gauze masks exercise a certain amount of restraining influence on the number of bacteria-laden droplets possible of inhalation.
And they point out that whether this will, in practice, actually reduce infections must be proved through clinical testing that demonstrates a reduction in the number of infections.
See the parts I highlighted there? If you want to prove something reduces infections, it’s really best to run an experiment where you get fewer infections.
It remains for future controlled experiments in contagious disease hospitals to determine whether the wearing of masks of such texture as to be reasonably comfortable are effective in diminishing the incidence of infection.
They made a conclusion that should come as a shock to no one:
Masks have not been demonstrated to have a degree of efficiency that would warrant their compulsory application for the checking of epidemics.
But the science is always changing, right? Jump forward a century and in 2020 the following literature review was published in the May-June issue of Salud Pública de México. The abstract is in English and the full article in Spanish. The quotes below are taken from the English language abstract, and the authors offer an interesting insight.
2. Rapid review of the use of community-wide surgical masks and acute respiratory infections (Stern et al., Salud Publica Mex. 20203)
The authors conducted a review of the scientific literature on masks and summarized several other literature reviews for us.
Of six systematic reviews, four found no reduction in the probability of transmission. Experimental home studies found no differences in the probability of contagion associated with the use of mouth masks. Only one modeling study estimated a 20% reduction in the incidence of acute respiratory disease, assuming that 10 to 50% of the population use the surgical masks correctly.
If you read my last post (you masochist) then you know my opinion already on modeling studies - their output is dependent on their input, and often must make an assumption about effectiveness to produce their prediction.
We’ve looked at literature reviews before but this one has a fun little observation. The authors point out that “natural experiments” are occurring in other countries and advise waiting for results from those experiments before deciding.
The scientific evidence is inconclusive to recommend or discourage the use of surgical masks at the population level. Considering the potential negative effects, official recommendations should await for the results of natural experiments currently occurring in countries that have recommended the use of face masks at the population level.
It is now one hundred years later, and only a very small number of the experiments suggested by Kellogg & MacMillan have been conducted, and the results are still inconclusive. But the good news is, you get to be the guinea pig in a population-wide experiment! Of course there are no controls in this big experiment so the results will still be useless.
Conclusion to this huge mess, along with the obvious recommendation that we should take the CDC behind the woodshed for a little parental feedback.
The CDC decided to prank everyone in the country by telling us to wear pieces of cloth over our mouths, and had their intern put together a whole, carefully researched web page about it (with references!). The intern referenced articles and studies that for the most part don’t address the effectiveness of masks. The handful of mechanistic studies show what one would expect - masks filter particles, which is what they were designed to do.
But the CDC (I mean the intern) is silent on the subject of randomized controlled trials. In some randomized controlled trials health care workers see a small benefit (although in most there is none), but in some of those studies the participants are trained in infection control procedures and may be using other forms of protective equipment. Studies in the community setting for the most part show no benefit, and many of those combine mask wearing with hand hygiene. Some of the studies even had negative outcomes for some mask wearers.
The CDC fails to mention any of these studies despite having paid for some of them.
Several literature reviews have also concluded there is no solid evidence of a benefit, including the recent review by the World Health Organization.
So why exactly do we have a thing called the CDC? We give them money, which they use to finance research that they proceed to ignore when it suits them. Instead, with little evidence of a benefit, they encourage local governments to engage in a large scale medical experiment based on nothing more than theory (and maybe some peyote, who knows what they really spend their allowance on). I suggest we donate the entire CDC to someone we don’t like and forget about them. Maybe we can get a tax write-off.
Please feel free to wear a mask if you still want to - but leave the rest of us alone. Live, and let live.
Even Dharma understood that much about life, and she was just a character on TV.
Kellogg WH, Macmillan G. AN EXPERIMENTAL STUDY OF THE EFFICACY OF GAUZE FACE MASKS. Am J Public Health (N Y). 1920;10(1):34-42. doi:10.2105/ajph.10.1.34
https://pubmed.ncbi.nlm.nih.gov/18010229/
J. Flint, V.R. Racaniello, G.F. Rall, A.M. Skalka. Principles of Virology, Fourth Edition, Bundle. American Society of Microbiology (2015). doi:10.1128/9781555819521. ISBN 978-1-55581-952-1.
Stern D, López-Olmedo N, Pérez-Ferrer C, González-Morales R, Canto-Osorio F, Barrientos-Gutiérrez T. Rapid review of the use of community-wide surgical masks and acute respiratory infections. Salud Publica Mex. 2020;62(3):319-330. doi:10.21149/11379
https://pubmed.ncbi.nlm.nih.gov/32272522/