At the time of the balance sheets, after three years of pandemic, some question the relevance of the measures adopted to curb the transmission of SARS-CoV-2, responsible for COVID-19. Even the effectiveness of the mask is challenged by one of the authors of a literature review published by the renowned Cochrane Library. Have we taken the wrong road by requiring everyone to wear a mask, by establishing confinements?
In a notable media release, Tom Jefferson, first author of the “meta-analysis” to assess the effectiveness of physical measures in reducing the spread of respiratory viruses which was published last January in the Cochrane Library, said that there is no evidence that the mask is effective. It was enough for the assertion that the mask does not work to spread. An opinion column published in the New York Times of February 21 drove the point home by affirming, with supporting quotes from Jefferson, that the obligation of the mask had produced nothing and that lessons had to be learned from it.
The mask is effective, but you have to take the trouble to wear it correctly
Real stone in the pond, these declarations delighted the groups opposed to the measures, which finally found an echo in their convictions. They also reacted to scientists accustomed to rigorous publications from the Cochrane, a non-profit organization based in the United Kingdom and composed of an international network of researchers, health professionals and patients, including publications summarizing the best research evidence are considered a reference for health professionals.
As history began to stir, on Friday March 10, the Cochrane Library’s Editor-in-Chief, DrD Karla Soares-Weiser, issued a warning: “Several commentators claimed that a recently updated Cochrane review showed that ‘masks don’t work’. This is an inaccurate and misleading interpretation,” she wrote. “It would be more accurate to say that the results of the review – which examined whether wearing a mask slows the transmission of respiratory viruses – are inconclusive. It does not make it possible to determine whether wearing a mask reduces the risk of contracting or spreading respiratory viruses, ”she continues.
Limits of the journal
“By shouting loud and clear that the mask was not effective, Jefferson went beyond what the data in his review allowed him to say”, claims Geneviève Marchand, researcher in the prevention of chemical, biological, mechanical and at the Robert-Sauvé Research Institute for Occupational Health and Safety.
The scientist points out that the Cochrane Library’s meta-analysis reviewed data from various research “which did not have the same objectives”. For example, some were about COVID-19, others about the flu. However, we have learned that the viruses causing these two respiratory diseases are very different: SARS-CoV-2 is much more contagious and spreads in fine droplets which remain suspended in the air much longer than larger droplets. containing the influenza virus, which, due to gravity, do not travel as far through the air. These differences would likely explain why mask benefits have been harder to detect in flu studies, Columbia University scientist Lucky Tran points out in The Guardian.
Another problem with the review: less than 50% (only 42.3%) of the participants who had to wear the mask followed the instructions. “It becomes difficult to demonstrate the effectiveness of the mask if people do not wear it”, notes Mme Merchant.
In addition, several studies have compared the effectiveness of the mask in populations that were vaccinated. “In such a situation, as people are less at risk of developing the disease, it becomes more difficult to demonstrate that the means of protection, in this case the mask, is effective,” points out Ms.me Marchand, before launching that “the medical mask and the N95, which is a respiratory protection device, are tools that are efficient and which we no longer have to demonstrate”.
wear it well
According to Benoît Mâsse, professor at the School of Public Health at the University of Montreal, “it is very difficult to have certainties, evidence, and to conclude on the basis of observational studies [comme celles revues dans la méta-analyse Cochrane] “.
He draws a parallel between wearing a mask and wearing a condom to protect against HIV. “At the start of the HIV pandemic, we knew that condoms were very effective in preventing the transmission of HIV. We have therefore carried out campaigns and interventions to promote its use. However, we realized that at the population level, it had no effect, it did not reduce the transmission of HIV in a population. Does this mean that the condom does not work? Rather, it was not used at all, or misused. If 50-70% of people are wearing it improperly, I have no trouble believing it won’t offer any protection. It’s the same for the mask. Laboratory studies in which the mask is worn well and fitted well have shown its effectiveness. It is a tool that, if worn correctly, will protect us,” he explains.
In several regions of the world, particularly in Asia, where people were already wearing it before the pandemic, people who take the trouble to put on a mask wear it much better. They are more rigorous, perhaps because they were used to it, he points out.
“The population should not have completely lost confidence in the mask on the basis of [cette étude]. Unfortunately, I fear that it will feed movements that question everything that has been done during the pandemic, ”says Mr. Mâsse.
“The mask is effective, but you have to take the trouble to wear it correctly, he underlines. But I have no doubt that there is a large segment of the population who will not wear it properly if we declare a health emergency in a population like Quebec and we insist that everyone door. »