The authors of the new study are specialists working for Cochrane, the most respected non-profit organization that analyzes medical research. Specialists working on Cochrane reviews do not conduct experiments themselves, but analyze all or almost all relevant works on any topic – and based on the results of such an analysis, they conclude whether this or that drug or medicine really works. Cochrane reviews are considered the gold standard of evidence-based medicine, so they always receive a lot of attention both among specialists and in the media.
The review that resuscitated mask spores is titled Physical Interventions to Prevent or Reduce the Spread of Respiratory Viruses, and one of its findings is: “The pooled study results showed no clear reduction in respiratory viral infections with medical/surgical masks.” It would seem that everything is clear: masks do not work, the opponents of wearing them were right. But this is only at first glance. The authors themselves note that the reliability of the evidence they found in the studies studied is so low that it does not allow any reliable conclusions to be drawn.
It would seem that everything is clear: masks do not work, the opponents of wearing them were right. But this is only at first glance
Cochrane reviews are not a magical measure of ultimate truth. Their authors analyze the evidence that is presented in the currently available scientific papers, and if the quality of this evidence is low, then the final conclusion from them will be unreliable. Here, as in programming, the rule “garbage in, garbage out” applies.
The low quality of research on the effectiveness of masks is a known and most likely unresolved problem. Because the effect of wearing them is noticeable only after a sufficiently long time. To prove that mask wearers are less likely to get sick than those who don't, you need to follow the two groups for a long time, comparing the number of infections – and at the same time be sure that people who claim to use masks really wear them all the time when appear in public places. And how can you check it? Given the low budgets that can usually be obtained for this kind of research, a typical method of verification is a survey. And this immediately introduces a huge factor of uncertainty.
The lying factor can vary markedly depending on social stratum, age, and even occupation.
In 2021, scientists conducted a study in Kenya, the purpose of which was to estimate the size of this factor and find out how many of those who claim to wear a mask all the time actually do so. Adherence to the mask regime was declared by 76% of respondents in Kenyan rural settlements, while observing people in public places, scientists calculated that it is actually correct – that is, covering the mouth and nose and not removing it when talking – wear masks only 5.7 %.
The lying factor can vary considerably depending on the country, social stratum, age, and even occupation – for example, doctors, on average, wear masks or respirators much more disciplined than representatives of other professions. Some studies take this into account, but often scientists analyze the effect of wearing masks in general in society, therefore, it is impossible to understand what percentage of participants were telling the truth. Which, of course, affects the results: if you analyze the bases of scientific articles, you can find many works similar in design, the authors of which came to opposite conclusions.
Lies about mask adherence are not the only reason why different studies show different results. This situation is often observed when, in addition to the effect being studied, something else affects the outcome – in this case, the probability of infection. In the case of masks and coronavirus (although the Cochrane experts in the review analyzed works studying the effect of masks on the spread of various respiratory infections), one of the most important additional impacts is vaccination. Moreover, it can influence in different directions. Some of the people who have been vaccinated against covid are cautious people, they are afraid of getting sick and carefully wear masks. Others, on the contrary, after the vaccination felt safe and stopped worrying about additional protection measures.
Lies about mask adherence aren't the only reason studies are showing mixed results.
Other factors that affect the overall effectiveness of masks in preventing transmission are the contagiousness of the virus, the prevalence of the pathogen in the population, and the behavior of others. It is very difficult to take into account all these parameters and isolate the effect of masks. Especially if we want to find out their impact not on the risks of infection of an individual, but on the spread of respiratory diseases in general – which is what the authors of the works analyzed by Cochrane experts did.
This is a very important point that critics of the masks, who use this review as an invincible argument, omit or do not understand. Cochrane was only interested in work that studies the effectiveness of masks at the population level as a means of public health, and not personal protection. And in this capacity, due to the influence of all those factors that we talked about above, masks cannot be considered a guaranteed remedy, much less a panacea – at least if their wearing is not strictly controlled. At the same time, they can work as an additional element that reduces the risks of spreading infections when other measures are applied.
As a public health tool, masks cannot be considered a guaranteed remedy, much less a panacea.
When it comes to personal protection, the picture is completely different. In laboratory studies, when scientists spray mannequins with aerosols of varying droplet sizes, or assess how much less droplets fly out of the mouth and nose with and without a mask, they clearly see that masks trap most of them, especially if they are worn by all participants in the communication. That is, technically masks work, another question is how they are used in the real world.
If you are the only person wearing a mask in a crowded, unventilated area, if you are not vaccinated and there is a lot of circulating virus and it is very contagious, if you are in such conditions for many hours – the mask is unlikely to save you when there are carriers of the virus in the same room . But if you are vaccinated and the circulation of the pathogen is not so high, if half the people are wearing masks, and you have been in such a place for only half an hour – a mask can significantly reduce your risk of infection, even if there are infected people in the same room. In the same way, for example, a helmet will save you if you carefully ride along a bike path in a park at low speed, but it will hardly help if you jump out on a bike at night on the Moscow Ring Road.
Finally, there is another factor that cannot be ignored. It is believed that Cochrane reviews are an absolutely objective thing, but this is not so. They are also written by people, and often, if the topic is quite narrow and also polarized, like the question of masks and their effectiveness, the likelihood that among the authors there will be a noticeable percentage of representatives of one of the camps is high. And this is exactly what happened with the mask review: at least two of its authors are opponents of masks, and the head of the study, a well-known scientist in his field, during the pandemic caused, to put it mildly, the surprise of his colleagues, as he stubbornly insisted that the coronavirus was not transmitted by aerosol, and, accordingly, masks cannot protect from it by definition. This is a marginal point of view,there are a lot of well-designed studies proving the aerosol transmission of coronavirus, and the question arises: how did a person with such unconventional views end up among the authors of the review.
The project manager surprised colleagues by insisting that the coronavirus is not transmitted by aerosol
Summing up. The Cochrane Review added nothing to our current state of knowledge about masks and their effectiveness as a means of protecting against infection with respiratory viruses. Physically, the mask, working as a barrier, reduces the risk of infection transmission. But everything matters: what kind of mask you wear, whether you put it on correctly, whether you wear it all the time while you are indoors with other people, or lower it to talk and eat, how often you go to public places, how contagious the virus is. , whether you have proper immunity to it (if so, then a small amount of particles that will penetrate your mucous membranes, despite the mask, will be successfully destroyed by immune cells and antibodies), finally, how many people around you wear or do not wear masks and what is the the circulation of the virus at the moment … And we are talking only about personal protection!
At the population level, much more important than masks is the behavior of people, the level of vaccination, other epidemiological measures taken by governments. The spread of pathogens is a multifactorial complex process that depends on many input conditions that are often difficult to measure.