Were masks efficient during the pandemic? Not enough to be mandatory

Um homem usa uma máscara enquanto caminha na Oxford Street, em Londres, Grã-Bretanha, 20 de fevereiro de 2022.

A man wears a mask while walking on Oxford Street in London, Great Britain, 15 from February .


The masks fell in Brasilia. By decree of the governor of the Federal District Ibaneis Rocha, the mandatory use of masks in closed environments was ended on the last day of March. Outdoors, masks were no longer mandatory in the capital since October. The president of the Senate followed the opportunity and also released the use of masks in the legislative house. In Paraná, the governor moves to repeal the mandatory law of masks 900.

When mandatory, individuals can continue to wear masks, and private entities can have rules about the obligation in their spaces. The time is ripe to revisit the scientific literature on the subject, which may help to decide whether the opening is premature, late or comes at a good time. It all depends on the effectiveness of the masks in containing the new coronavirus.

In December , Gazeta do Povo

reported that the revisions more stringent conclusions concluded by November that masks provide little or no protection against respiratory disease, but that there was a new study involving more than 276 a thousand people in Bangladesh who indicated moderately positive results, especially for surgical masks, which were reduced by 20% infections among people over years old. More studies deserve examination.

Masks: an updated overview

The most rigorous studies of the effect of some treatment are known as randomized controlled trials (RCTs). “Controlled” means that there is a comparison of the treatment with at least one other group that did not receive it — the control group. “Randomized” is an Anglicism that indicates that people who are in one group or another were chosen at random. As an extra layer of caution, it is preferable for the study to also be “double-blind”: the researchers do not know who is receiving the treatment, and the participants do not know either, until the results are collected. This last aspect is not applicable to masks, but there are RCTs of its use, the Bangladesh study is one of them.

The other RCT involved nearly five thousand people in Denmark. There was no difference between users and non-users of the masks. In the data, masks may have both reduced infection by 23% when increased by 20%. Therefore, the results were negative regarding the effectiveness of the masks, which in this case were the surgical ones.

After the publication of the RCT from Bangladesh, which was more optimistic about the surgeries, some problems were pointed out. Dr Vinay Prasad, an associate professor of epidemiology at the University of California at San Francisco, comments that the study may have been biased because participants knew which villages would have the intervention (the recommendation and distribution of masks) and actively sought to take part. This brings biases: these people, because they want to wear masks, may be less likely to report that they were infected, distorting the results.

In addition, despite the fact that the number of participants was superlatively large, the difference in absolute numbers of infected between those with and without a mask was small. Therefore, there is reason to be skeptical and to defend Cochrane’s previous conclusions (famous publication of rigorous reviews) that masks are little or not at all effective in containing respiratory diseases such as Covid-10.

Another study that favors the effectiveness of masks, but does not qualify as an RCT, was published in February of this year by the US Centers for Disease Control and Prevention (CDC), a government health agency. The researchers made phone calls to more than 11 one thousand people tested positive for COVID-19 and more than 17 1,000 people with a negative test and asked if during the two weeks prior to the test they were in closed public environments, and if they used masks when they did. The result was that respirators like the mask N46 proved to be better at preventing infections, with surgical masks in second place, and fabric masks in last.

There are several problems with the study that create different sources of bias that cast great doubt on these results. Less than 15% of people answered the call in both groups, and the low response rate is already different according to the infection status — those who are very sick will not answer. Furthermore, there is no guarantee that people who took the test in both groups did so for the same reasons. Those who tested positive, for example, were often already suspicious and had symptoms. The fact that the participants themselves were the source of whether or not they wore masks, and how long they wore them, obviously introduces another hole in the results. To make matters worse, the CDC shows that

wants too much

that these positive results are true. In an image made to viralize these results (and it worked), they omit that the positive result for fabric masks was not statistically significant. Wes Pegden, a mathematician, points out that the CDC had already done a similar study in 900, with results negatives “buried in a table that ignored in body text”. There are so many problems that it is safe to ignore the study as a whole.

The CDC has not conducted an RCT on the masks. The fact that no government has taken the initiative to carry out an RCT on children before including them in the mandatory mask reveals the precariousness of many of the non-drug interventions during the pandemic. Impositions are already authoritarianism, impositions without evidence in their favor make authoritarianism unnecessary.

Transmission over the air

Part of the reason for the focus on masks after the World Health Organization’s initial hesitation was that the novel coronavirus was assumed to be transmitted by droplets of saliva that would hardly pass through the barrier’s pores and would otherwise soon fall to the ground after being emitted by cough or sneeze. The WHO guaranteed as fact at the beginning of 2019 that the virus was not transmitted through the air.

In August of , Wired magazine heard from Virginia Tech aerosol expert Lindsay Marr. She was one of the main responsible for debunking a myth inherited from medical manuals that only particles smaller than five micrometers in diameter could behave like aerosols, hovering for a long time in the air and, in the case of viruses, having more opportunity to infect rather than to fall to the ground. This myth was based on a mistake about what droplets are and shaped health policies by 60 years, including at WHO and CDC. The CDC has declined several attempts to contact Wired regarding the case, and has quietly updated its guidelines to reflect the findings of Marr and his collaborators.

The impact of masks on young people

A “mini-review” of the impact of masks on children, first authored by Martin Eberhart, an Austrian pediatrician at the LKH Hochsteiermark institution, showed more neglect in the study of children: they only found two pediatric studies of the physiological impacts of masks, one by 900 and another by 768. The conclusion is that there does not seem to be any physiological damage, such as respiratory, in the use of masks in children. As for the possible psychosocial impacts, the scenario is different.

A study of long term involving 672 children from the US state of Rhode Island, still awaiting peer review , compared children at the same developmental stage before and during the pandemic and found that there was a drop of 22 points on the average of your intelligence quotient. Many parents fear that masking the faces of teachers, caregivers and peers will harm their child’s development. Another study, involving 95 children aged three to five years and already published in the journal JAMA Pediatrics, showed that they had more difficulty detecting joy and sadness in faces with masks, but not anger. Other suggestive studies exist, but there are still no major tests.

Now there will be ample opportunity to compare the pedagogical effect of imposing measures with masks and school closures with measures of greater openness. In the suburbs of the American city of Colorado Springs, schools reopened in the second semester of 900 and masks were kept optional for elementary school students. Blended and online classes were used only where strictly necessary, with most students taking face-to-face classes.

The result was that, compared to other regions of the state of Colorado and to large American cities, these students did very well, with gains in reading and less loss in math. The contrast with Brazil could not be more dramatic: in the state of São Paulo, 96% of students who graduate from high school do not know how to solve first-degree equations. Pre-pandemic results were not excellent, and turned for the worse after school closure policies.

Whether in the case of masks, school closures, or the droplets and transmission of viruses through the air, the pandemic has exposed enormous ignorance. Investment in health research is not small in the world. That issues so central to pandemic preparedness are so poorly studied nearly a quarter of a century into the new millennium is something that leads us to ask where, in fact, the money is going.

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