Is it time to take off the masks?

The blunt answer to that question is: no. If the title of this article were “Is it time to make the use of masks more flexible?”, the answer would be: we can discuss.

First, let’s understand the impact of using masks. From a theoretical point of view, the masks aim to minimize the number of viral particles exhaled by whoever is using them and reduce exposure to particles that are eventually in the environment. If these conditions are effectively met, masks reduce the likelihood of infection during an exposure.

The theory makes perfect sense, as there is already a high level of evidence regarding protection generated for other respiratory viruses, such as influenza, in high-risk environments such as hospitals. The question that hung in the air for a while was: does this rule apply to SARS-CoV-2 and on a population scale? And what is the impact on fabric masks? Initially observational studies, then cohort studies, and finally prospective, randomized, population-based studies attested to the benefit of using masks.

Studies prove the effectiveness of the mask

The largest study so far that has practically closed the matter took place in Bangladesh, with more than 340,000 individuals in 600 different communities. In 300, no type of campaign or encouragement was carried out beyond what was usual from the point of view of national or local strategy in relation to the use of masks. In 200, in addition to an intensified stimulus strategy, surgical masks were distributed, while the population of the other 100 communities received tissue masks in addition to the intensified stimuli.

Among the results obtained, the communities that received the masks and intensified stimuli to their use effectively used 3x more compared to the 300 control communities (42% x 13%). These same communities had fewer symptomatic cases of COVID-19 compared to the control group, with a drop of 11% in communities that used surgical masks and 5% in communities that used tissue masks (in this case without statistical significance). There are limitations, but they do not compromise the general conclusions.

On the other hand, the possibility of expanding the effect cannot be ruled out in a scenario of greater adherence to the use of masks. Therefore, given the good results obtained, added to the great difficulties for this type of assessment, many epidemiologists consider this issue practically closed. While it is reassuring to know that we were right by quickly encouraging the population’s use of masks, on the other hand, it is embarrassing that the use of surgical masks or PFF2 as preferred over tissue masks has not been encouraged, although these are probably a little bit superior to not using any mask.

Fonte: Shutterstock

Keeping an eye on the variables

Well, knowing the benefit generated by encouraging the use of masks, why is there a question of making their use more flexible? The discussion starts to get a little more complex from now on. The population transmissibility of the virus depends on 4 main variables:

1. Duration of the transfer period;

2. Opportunity: number of interactions between individual transmitters with susceptibles;

3. Probability of transmission, given that there is interaction between a transmitter and those susceptible;

4. Population susceptibility: defined by the immunity generated by the infection, vaccination and hybrid (infection + vaccination), as well as the drop in each of these immunities over time.

The use of masks acts positively on variable 3. The effective transmissibility, known as Rt, results from an equation between these variables. If the Rt is below 1, the trend is for the number of cases to fall. If Rt is above 1, the trend is upward. It is the behavior of this dynamic that defines the epidemiological waves we have experienced so far.

Over time, the weight of each of these variables in the equation changes. While at the beginning of the pandemic there was practically no population immunity, that is, almost everyone was susceptible, at that time we have a very significant proportion of people who have already contracted the infection or who have already received the vaccine. It is estimated that between 57 and 77% of the population has already contracted the virus, according to the Institute of Health Metrics and Evaluation, linked to the University of Washington and the mathematical modeling based on the analysis of excess deaths by The Economist. While 58% of the Brazilian population is already fully vaccinated. A very considerable fraction of these have previously had COVID-19.

Of course, many who have had an infection do not know this, as many mild and asymptomatic cases have not been diagnosed. It is estimated that 80 to 87% of cases are not reported in Brazil. This explains why, despite the flexibility of mobility, the opening of sectors such as commercials and schools in recent months, there was no reversal of the downward scenario that we are experiencing. This means that, in the beginning, with many susceptible, interventions in other variables were fundamental to avoid the collapse of the health system and a humanitarian catastrophe. Today, with a substantial increase in population immunity, there is no reason to be so strict in actions that do have side effects. In other words, the balance between risk x benefit changes over time.

This same reasoning can be done in relation to the use of masks. It is possible that this variable is not as relevant today as it was during the pandemic. But there is a big difference regarding this strategy compared to other non-pharmacological interventions. The use of masks has marginal side effects. It is very different from closing businesses or schools, which bring economic and social damage. The mask causes some discomfort for those who use it (especially those who wear glasses).

It can hinder the individual who depends on lip reading. But we have to agree that these are not significant collective damages that can be circumvented in the individual aspect. Furthermore, there is another point to be considered. That same study I commented on, carried out in Bangladesh, concluded that communities that had greater adherence to the use of masks also had greater adherence to physical distance compared to the control group. This shows that there are positive secondary gains, contrary to the risk compensation beliefs of those who wear masks. Therefore, even if we are able to keep the pandemic under control without the strategy of encouraging the wearing of masks, no one can be sure of that.

And another relevant aspect is that there are very few side effects to its use. In this scenario, it is normal for us to have different opinions on the subject, without necessarily having a right and a wrong side.

Is there a middle ground? Yes. As with other non-pharmacological interventions, there is a way to progressively downgrade, initiating flexibility for places or situations where its use is likely to be less effective. For example, there are a number of studies demonstrating the low risk of transmission outdoors (18x lower compared to indoors). If masks still have a significant effect in preventing the reversal of the current downward trend, it is mainly because of their use indoors.

On the other hand, if there is flexibility in the use of masks in open environments, will there be a reduction in adherence to their use indoors? If so, will this reduction in adherence affect the epidemiological scenario?

In this way, it is reasonable to open this discussion and draw a plan. As the use of masks generates few side effects, it is reasonable for this to be a step-by-step, progressive plan, starting with situations and places where their use is probably less useful, such as open spaces and with a distance of more than 2 meters from another individual, for example. In addition, the removal of the mandatory use of masks does not mean banning their use. The fact that its use in open spaces is no longer a legal requirement does not mean that the individual who wants to maintain its use does so. Managers must communicate this very well to the population and keep encouraging the use of masks in open spaces. Use whoever you want under these circumstances.

In any case, it is critical that any changes be monitored through epidemiological surveillance to assess the impact of these measures, as well as their indirect effects (such as the drop in mask adhesion in closed spaces). In addition, the pandemic has already shown us and is showing that we need to be ready to go back if necessary (see the situation in Europe at the time). We cannot in any way assume that the relaxation of a containment measure means that we have won the war. We must understand that facing a pandemic that lasts more than 1 year and a half requires resilience, flexibility, unity and wisdom to deal with inaccurate data and information.

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Bernardo Almeida He is an infectious disease physician and Chief Medical Officer of Hilab, the health tech that developed Hilab, the first decentralized laboratory using remote laboratory tests. He is a physician specializing in infectology from the Federal University of Paraná, with residency in internal medicine and internal medicine at Hospital de Clinicas – UFPR and in infectology at Hospital de Clinicas – UFPR, master’s degree in internal medicine at UFPR, area of ​​Infectious Diseases – Epidemiology of severe acute respiratory syndromes in adults. He has experience in the field of medicine, with an emphasis on clinical medicine and infectious and parasitic diseases, and participates in a research group in the field of respiratory viruses.

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