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Unsuccessful COVID-19 mask attempt shows why more masks are needed



Back in the early days of the COVID-19 pandemic, researchers in Denmark decided to conduct a usual experiment to test infection control of face masks in the same way as they would evaluate a potential vaccine or drug.

At that time, masks were not recommended by Danish health authorities, and less than 5% of residents used them outside hospital settings. These conditions made it possible to conduct the first – and only – randomized controlled examination of the face covering.

The researchers recruited more than 6,000 volunteers from across the country who spent at least three hours each day with people from other households and did not wear masks to their jobs. About half of these volunteers were randomly selected to receive 50 surgical face masks and were asked to wear them when they left home for the next month. The other half did not get masks and served as controls.

Overall, 95 of the 4,862 volunteers who reached the end of the study became infected with SARS-CoV-2, the coronavirus that causes COVID-1

9. It is an infection rate of just under 2%.

But no matter how the researchers cut and cut their data, they could not find a strong signal that the volunteers in the mask group were more protected than their colleagues in the control group.

In a typical clinical trial, this is the point where researchers would say that their intervention did not work. But in this case, investigators went the other way.

The problem, they said, was not with the masks. The problem was that people did not wear masks enough.

The study results “should not be used to conclude that a recommendation to everyone to wear masks in society would not be effective in reducing SARS-CoV-2 infections,” wrote the team led by researchers from Copenhagen University Hospital.

A trio of current and former editors of the Annals of Internal Medicine, the journal that published the study, went further.

“Masks are likely to be worn by most, if not all, to reduce the number of infections in society,” they wrote. “The results of this experiment should motivate widespread mask wearing to protect our society and thereby ourselves.”

It is not as if there is no reason to believe that face masks can prevent the spread of COVID-19. Researchers say that coronavirus moves from person to person mainly through the air, either on respiratory droplets or smaller aerosolized particles. If one of these finds its way into the airways, an infection can take off.

People with active infections are most contagious in the first few days after exposure, often before developing symptoms. That’s why the World Health Organization, the U.S. Centers for Disease Control and Prevention, and other public health agencies say it’s important to wear a mask when in close contact with people from other households, even if you don’t feel sick.

Widespread mask use is credited for keeping COVID-19 deaths in the two-digit locations such as New Zealand (25 deaths to date), Singapore (28 deaths) and Vietnam (35 deaths). In Taiwan, where officials stepped up masking production just weeks after the WHO announced the existence of the new coronavirus, only seven people have died from COVID-19.

“The use of face masks has emerged as a powerful tool to reduce the pandemic’s health and economic damage,” said Dr. Thomas Frieden, a former CDC director who now heads the nonprofit health initiative Resolve to Save Lives, and his colleague Dr. Shama Cash-Goldwasser wrote in a comment accompanying the investigation.

If masks work so well, why did they make so little difference in Denmark? The study authors and their allies offer several explanations.

The experiment was performed in two waves, with the first group test masks between April 14 and May 15 and the second group testing them between May 2 and June 2. Most of the time – until May 18 – restaurants and cafes in the country were closed. The shops were open and public transport was in operation, but customers advised to maintain social distance. In addition, there were restrictions on social gatherings as well as visits to hospitals and nursing homes.

With all these measures in place, the added benefit of wearing masks can be negligible when the prevalence of the virus in society is low, the researchers wrote. (At the time of the study, the daily incidence of new infections was four times lower in Denmark than it was in the United States)

Masks are believed to help in two ways. Although they can protect carriers from the incoming bacteria, their primary benefit is their ability to prevent the carrier’s bacteria from spreading to others.

As few Danish residents wore masks during the study period, volunteers were mostly exposed to maskless people who could easily spread a virus – and this was true, regardless of whether they were randomly assigned a mask or not.

Another problem is that people who are required to wear masks often choose not to do so. Only 46% of volunteers in the mask group told the researchers that they followed all the rules about wearing masks in public, 47% said that they “predominantly” wore their masks, and 7% said that they did not follow the rules.

In other words, the journal editors noted, “The study examined the effect of recommending the use of masks, not the effect of actually wearing them.”

There is also the possibility that people wearing masks felt a false sense of security and failed their guard in other ways that increased their risk of infection.

Given these various shortcomings, you might suspect that the editors of the Annals of Internal Medicine were tempted to reject the study so that it would not fall into the hands of ever-higher opponents of mask mandates. They do not blame you for wondering – they actually expect this issue in their editorial.

With strong opposition to masking recommendations from leaders and the public in some localities, is it irresponsible for Annaler to publish these results, which could easily be misused by those who oppose masking recommendations? We do not believe, ”wrote Dr. Christine Laine, the magazine’s editor-in-chief, along with Dr. Eliseo Guallar, Deputy Editor of Statistics, and Dr. Steven Goodman, a former senior statistics editor for the journal.

Burying the results of a well-conducted study that did not turn out as expected would be worse, they wrote.

“We need to gather a lot of evidence to solve the riddle of how to manage the SARS-CoV-2 pandemic,” they explained. “For this reason, we felt it was important to publish the results and carefully highlight the questions that the trial does and does not answer.”

Frieden and Cash-Goldwasser agreed that researchers still have a job to do.

But in the meantime, they wrote, the bottom line is clear: “If everyone wears a mask when they are near others, everyone is safer.”




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