Why Masks Work

I’m sick of COVID19. I wish it would just go away. I want to go to live concerts, send my kids to school, shake hands with people. But denial isn’t going to make this virus go away.

We need both faith and science to get through this. Faith gives us hope and optimism, and motivates us towards altruism and pulling together with our collective humanity.

We also need to engage rationally with what’s going on worldwide and objectively examine the evidence on how best to get through it while minimizing the health and socioeconomic impacts. In order for science to help us, we have to be willing to change our previously held conclusions when new evidence comes to light.

Photo courtesy of pixpoetry, on unsplash.com

Early on in this pandemic, experts didn’t recommend everyone wear face masks, but also left the door open to the fact that future data might change their minds. And that’s exactly what happened. Early on, there were a lot of valid unanswered questions- would masks make people touch their faces more and therefore get the virus more often? Would COVID19 be too small for masks to stop? If everyone wore a mask, would there be enough for those treating sick patients in the hospital?

Flattening the curve bought us time to gather evidence to answer some of those questions. The recommendations were changed with the evidence that masks are better than we thought they would be, even with a tiny virus like COVID19, and that spread by touch doesn’t happen as often as it does through respiratory droplets, and that even home-made or other cloth masks are effective.

Understandably, people get confused when scientists say “We don’t have the evidence to recommend everyone wear a mask” one month and then turn around and say, “We recommend everyone wear a mask” the next. But that’s how science works. When good evidence contradicts our previously held conclusions and it’s verified by multiple studies, we change our views.

Experts changing their recommendations based on new evidence is not a sign of ineptitude, it’s the result of correctly applying the scientific method. People changing their minds to follow those recommendations after critically evaluating information and considering its source is not gullibility or being “sheeple”, it is a sign of health literacy. That’s totally different from blindly accepting what lay people say on Facebook.

I invite you to consider the following evidence gathered from the many studies that support the recommendation for the public to wear masks.

We’ve learned that COVID19 is mainly spread through droplets of moisture that are expelled in our breath. This happens even with simple talking, singing, heavy breathing, coughing or sneezing. You can see how these microscopic respiratory droplets spread in this video from Intermountain Healthcare, and how a mask decreases their spread.

Another way to visualize this is seen in this video which uses laser light scattering. This video is from a study published in the New England Journal of Medicine.

Any of your respiratory droplets could be carrying COVID19 and you wouldn’t have any idea. When those droplets enter someone else’s nose, they get it.

It should be fairly self-explanatory how masks work, but here’s the science behind it: Water droplets in our breath quickly evaporate to a smaller size as we breathe them out. The faster they dry out, the smaller they become and the farther they can travel. When we wear a mask, the thin layer of air between our face and mask remains humid. The water droplets remain large and heavy and are either trapped completely by the mask or fall much more quickly to the ground if they escape. A Cornell University study showed that respiratory droplets expelled from a person wearing a mask traveled an average of only 1.5 meters instead of 5 meters.

Also, we realized that in our research, we were asking the wrong question early on– ‘will a mask keep the wearer from getting COVID19?’.  Then researchers started looking at ‘will a mask keep the wearer from spreading COVID19?’. It turns out cloth and surgical masks are much better at the latter (source control) than the former (PPE). Surgical and cloth masks are adequate to slow down and immobilize the large droplets between your face and mask, but small particles that travel far enough to make it from someone else to you can still get through your mask. That’s why experts said early on that surgical masks aren’t adequate to protect you from getting COVID19- the virus is small enough to get through the mask fabric (unless it’s still trapped in a droplet of moisture). That also illustrates the fact that the more people who wear masks, the more effective an intervention it will be.

If masks keeps respiratory droplets from spreading, that means virus particles don’t spread.

A study published in the journal Nature showed that surgical masks blocked the spread of seasonal coronavirus by nearly 100%, a much higher rate than influenza and rhinovirus. It would make sense for this to be true of COVID19 as well. In fact, a study in Beijing showed use of a surgical mask conferred a 79% reduction in transmission of COVID19 even with close household contacts. The protection was best if the mask was used before symptoms began.

But data is best trusted when replicated in multiple studies. A meta-analysis (study that compiles data from multiple other studies) recently published in the Lancet showed that use of surgical masks decreased transmission of COVID19 by up to 95%. This study also found that maintaining physical distance of 1 meter decreased transmission by 82%. Read some well done summaries of this study here, here and here.

Even if you don’t have a surgical mask, a cloth mask will block 75% of respiratory particles. The better masks have multiple layers of close knit fibers. For instructions on choosing or making a mask, check the John Hopkins website here. Even simple barriers like bandanas decrease transmission by 15-30%, but are still better than nothing. Adding a nylon layer boosts the protection of these masks by up to 30%. Cloth masks kept two COVID19 positive employees at a Great Clips in Missouri from spreading it to a single one of their 140 clients. (I still think they should have stayed home).

Overall, mask use by the public shows so much promise that a study using a mathematical model to predict what would happen if everyone wore a mask showed that they could potentially prevent second waves of COVID19 as effectively as lock-down. Mathematical simulations in which everyone wore a mask suppressed the R0 (the average number of people a sick person infects) to below 1, which is like holding the head of the virus in a population under water. It will eventually die out. Even if 50% of the population masked up, that would still be a significant benefit, allowing hospitals to treat the sick without running out of beds, ventilators, etc.

States with widespread mask use have had decreasing cases over the last 2 weeks.

There are implications for our local area. A study done in Saint George on May 9 showed that only 19% of people wore masks, and even fewer– 16% — wore masks on June 20. It is not a coincidence that local cases are accelerating in an exponential fashion. Dixie Regional Medical Center ICU is quickly nearing its capacity.

Angela Dunn, Utah state epidemiologist recently said, “We are in the acceleration phase of the COVID-19 outbreak in Utah…. We are quickly getting to a point where the only viable option to manage spread and deaths will be a complete shutdown. This might be our last chance for course correction. Contact tracing and testing alone will not control this outbreak.”

The course correction she was referring to, that could prevent another complete shutdown, is wearing masks.

3 Replies to “Why Masks Work”

  1. Wonderful article Dr. Larsen! I’m definitely sharing this with my missionaries and their families. Keep up the great work.


  2. Tim, I think your article on wearing mask is excellent. Is it OK if we send it to our mission presidentS and health Council’s? Also I think it would be worthwhile if you would use MD after your name. you say byTim Larsen. I think you should put, MD and do that at the bottom of it too.

    Sent from my iPhone



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