Expanding Our Understanding: Do Masks Work?

Wouter Rietsema, MD, Vice President Population Health and Information Services, AHMC & CVPH

There is growing evidence that some people who got infected with COVID-19 despite wearing a mask are still alive today because of that mask. And that gives us a new way of thinking about the protection face coverings provide.

From early on in the pandemic, you’ve heard from me, my colleagues here at CVPH and public health officials across the country bang the drum on the importance of wearing masks and how they can help slow the spread of the novel coronavirus. The initial selling point was to wear one to protect others around you. Any one of us could be infected with the virus and not realize it, because we are not experiencing symptoms (otherwise known as being asymptomatic). In fact back in March, I talked about getting into the behavior mindset of each of us acting as if we have it.

We know that masks can dramatically decrease the amount of infectious droplets coming out of our mouth and nose from getting into the air when we breathe, talk, cough or sneeze. That makes it harder to spread COVID-19 to others around us. As time has gone on and we’ve learned much more about the virus, a significant amount of evidence has shown that wearing a mask can reduce the risk of the wearer getting infected by at least 60%.

So, I wear a mask to protect you, and you wear a mask to protect me. And when I’m wearing a mask, I’m also protected from others around me. A great example of this was in Springfield, Missouri in May. Two hair salon stylists infected with COVID-19 appeared to avoid spreading the virus to 139 clients who were exposed. Everyone was wearing a mask. The CDC posted a study about that incident.

There’s another layer to this. Nothing is guaranteed to fully protect you from the virus. Even N95 masks can let some particles in. But, what if wearing a mask meant that you could avoid symptoms altogether instead of winding up on a ventilator in the hospital?

That question is why we need to re-think how we define whether masks work or not. If it’s simply about getting infected or not, they work more often than not. Though masks decrease your odds of infection, you can still catch COVID-19. However, if you further define it as whether a mask prevents severe illness, it becomes even more encouraging. And, the benefits are incredibly significant. More people wearing masks may mean less serious illness and death from COVID-19. That, in turn, leads to less strain on our hospital and our health care system overall, saves lives, and helps us better control the virus before a vaccine becomes available.

One of the many peculiarities about this virus is the wide range of symptoms an infected individual can experience, from none at all to life-threatening problems requiring hospitalization. This wide range pops up not just on a national scale, but in individual outbreaks.

In February, an outbreak hit the Diamond Princess cruise ship docked in Yokohama, Japan. Of the 634 people on board who tested positive, about 18% of infections were asymptomatic. Yet, a month later, 81% of the 128 people on an Argentinian cruise ship who tested positive were asymptomatic. Why was there such a huge difference in asymptomatic cases? According to a study on the inoculum of COVID-19 (the dose of the virus), the key was that on the Argentinian ship, surgical masks were issued to all passengers and N95 masks were given to all staff as soon as the first passenger became sick.

The impact of universal masking may be even more apparent in the cases of two food processing plants. In Oregon, 95% of the 124 cases at a seafood processing plant were asymptomatic, and just under 95% of 481 cases at a Tyson chicken processing plant in Arkansas were asymptomatic. In both cases, employees were required to wear face masks.

So how can masks help prevent people who do get infected from suffering more serious illness? The short answer is that while a mask may let in some viral particles, it prevents a larger amount from getting into your body. Your immune system begins responding as soon as a virus gets in. So, a smaller amount of virus makes it easier for your immune system to beat it quickly and avoid any symptoms from popping up. A larger amount of virus means the immune system can get overwhelmed, leading to much worse symptoms. The basic idea: the less virus you get, the less sick you get. And, that concept is pretty well established with other infectious diseases.

So when it comes to what the motivation is to wear a mask, ask yourself the following question:

Would I rather the worst-case scenario be:

1. I get infected but never get seriously sick

OR

2. I get infected and wind up in the intensive care unit of a hospital and possibly die

It’s a different way of thinking about masks. This isn’t just about protecting others. You can protect yourself. And, even if you do get infected while wearing a mask, you can avoid the worst of it.

None of this matters if you don’t select an appropriate mask and wear it properly. That includes making sure the mask covers your nose and mouth and fits snugly against the sides of your face without gaps. The CDC has more helpful guidance.

Please also keep in mind that there are other important steps you can take to lower your risk of contracting COVID-19 even further.

1. Keep following social distancing rules – staying at least 6 feet away from others.
2. Avoid large gatherings, especially indoors.
3. Wash your hands frequently with soap and water or hand sanitizer.