According to a review in the Journal Nature there are two continuing randomized trials, one in Denmark and the other in Guinea-Bissau. The article questions the ethics of conducting a randomized trial in such a poor African nation [a spoiler alert : yes, it's unethical].

It also quotes scientists lamenting the time constraints preventing them from conducting proper clinical trials.

No matter how much time they had, researchers wouldn't be able to provide a precise understanding of how masks limit contagion because the primary purpose off masks for the community is to stop the transmission of disease to others, regardless of how well it may or may not protect the wearer.

Early in the pandemic, medical authorities recommend that only sick people wear masks, so that they would not infect others, then it became clearer that people who were not yet showing symptoms, or had mild symptoms, were also infecting others.

That was one key reason that universal mask-wearing became recommended, to prevent transmission to others - what's known as source-control. Preventing the mask wearer from becoming infected, to the degree that happens, is a secondary benefit.

As detractors of mask point out - randomized studies that prove The effectiveness of masks are nonexistent.  That's because doing an informative randomized study of masks are nonexistent.

That's because doing an informative randomized study of masks for preventing transmission would present such major  scientific and logistical challenges that it is all but practically impossible.

To explain why, you need to know how randomized trials work and why are they so valued, and also why they are not the only form of scientific evidence.

To understand whether drugs and other medical interventions work, researchers rely on randomized trials that assign participants randomly to a group that gets the intervention and a control group that gets nothing or a placebo.

Otherwise, if we let doctors choose who they gave drugs to, they might pick sicker patients.  Or if we let  patients enroll as they wish, those who are already interested in healthy behavior may disproportionately choose to try the new drug.

Without randomization, it would be difficult to figure out if differences between the groups are because of the drug or because of various-preexisting characteristics of the patients - known as confounding factors.

Randomized trials look at the benefits of the intervention only for the person who is enrolled in the trial. It's not possible for them to conclude how effectively masks prevent community spread to others -people who are not enrolled in the trials.

The honor and serving of the latest research and publishing on Masks and Trials continues to Part 2.. The World Students Society thanks author Zeynep Tufekci


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