[Série] Are surgical masks really effective against COVID-19v?

At the time of preparing the balance sheet, and three years into the pandemic, some question the importance of the measures adopted to limit transmission of the SARS-CoV-2 virus responsible for COVID-19. Even the effectiveness of the mask was challenged by one of the authors of a literature review published by the renowned Cochrane Library. Did we take the wrong path by requiring everyone to wear a mask by establishing confinement?

In a noteworthy media release, Tom Jefferson, first author of “Dimensional analysis” It aims to assess the effectiveness of physical measures in reducing the spread of respiratory viruses, which was published last January in the Cochrane Library, and said there is no evidence that the mask is effective. It was enough to confirm that the mask does not work in diffusion. a opinion column Posted in The New York Times On February 21, he drove the point home by emphasizing, with supporting quotes from Jefferson, that mask compliance produced nothing and that lessons should be learned from it.

The mask is effective, but you have to take the trouble to wear it properly

Real stones in the pond, these statements delighted the groups opposed to the measures, which eventually found an echo in their convictions. They also interacted with scientists familiar with the rigorous publications of Cochrane, a non-profit organization based in the UK comprised of an international network of researchers, health professionals and patients, including publications that summarize the best research evidence that is a reference for health professionals.

As history begins to move, on Friday 10 March, the Cochrane Library Editor-in-Chief, Dr^Dr Karla Soares-Weiser, published a caution Several commentators have claimed that a recently updated Cochrane review showed that ‘masks don’t work’. This is an inaccurate and misleading interpretation. decisive. It does not make it possible to determine whether wearing a mask reduces the risk of infection or spread of respiratory viruses.

Review limits

“By shouting loud and clear that the mask was not effective, Jefferson exceeded what the data in his review allowed him to say,” claims Genevieve Marchand, researcher in chemical, biological, and mechanical prevention at the Robert Sauvé Research Institute for Occupational Health and Safety.

The scientist points out that the Cochrane Library meta-analysis reviewed data from different studies that “did not have the same goals”. For example, some were about COVID-19, others about the flu. However, we have learned that the viruses that cause these two respiratory diseases are very different: SARS-CoV-2 is much more contagious and spreads in tiny droplets that remain suspended in the air for much longer than large droplets containing the influenza virus, which, due to gravity, do not travel great distances. far in the air. These differences likely explain why it’s so difficult to detect mask benefits in flu studies, notes Columbia University scientist Lucky Tran Watchman.

Another problem with the review: Less than 50% (only 42.3%) of the participants who had to wear a mask followed the instructions. “It becomes difficult to prove the effectiveness of a mask if people are not wearing it,” notes M^I merchant.

In addition, several studies have compared the effectiveness of the mask in vaccinated populations. “In such a situation, since people are less likely to contract the disease, it becomes difficult to prove that the means of protection, in this case the mask, are effective,” notes the lady.^I Marchand, before its release that “the medical mask and the N95, which is a respiratory protection device, are effective tools and we no longer have to prove it.”

Wear it well

According to Benoit Mass, a professor at the University of Montreal’s School of Public Health, “It’s very difficult to get certainty, evidence, and a conclusion based on observational studies.” [comme celles revues dans la méta-analyse Cochrane] “.

Compare wearing a mask to wearing a condom to protect against HIV. “At the beginning of the HIV pandemic, we knew that condoms were very effective in preventing HIV transmission. So we launched campaigns and interventions to promote their use. However, we realized that at a population level, it had no effect, and did not reduce of HIV transmission in the population. Does this mean that condoms don’t work? Rather, they are not used at all, or they are misused. If 50-70% of people wear them incorrectly, I don’t have a hard time believing That it will not provide any protection. The same for the mask. Laboratory studies in which the mask was well worn and well fixed showed its effectiveness. It is a tool that, if worn correctly, will protect us, “he explains.

In many regions of the world, particularly in Asia, where people wore them before the pandemic, people who take the trouble to wear a mask are better wearing them. He notes that they are tougher, perhaps because they are used to it.

“The population should not lose complete faith in the mask based [cette étude]. Unfortunately, I fear this will fuel movements that question everything that was done during the pandemic,” says Mr. Macy.

And he confirms that “the mask is effective, but you have to take the trouble to wear it correctly. But I have no doubt that there is a large segment of the population that will not wear it correctly if we declare a health emergency in a population like Quebec and insist that everyone be at the door.”

Let’s see in the video