Face Masks: A Substitute For Herd Immunity?

Since this coronavirus pandemic hit, the phrase “herd immunity” has become common in our lexicon. It refers to a situation when a sufficient number of people have developed immunity to the virus that they cease being viral reservoirs who can spread it to others. The point is that sufficient herd immunity will provide a significant block to further viral spread in the community. It is too dangerous to develop natural herd immunity by natural exposure to the virus; therefore, a vaccine is the best way to ensure herd immunity, but that is a year, probably longer into the future as reported earlier in these pages.

The virus has proven to be highly contagious, more so than your typical seasonal flu. An infected person can be expected to pass the virus to up to four other individuals, whereas the flu is typically spread to only two or fewer others. This, plus lack of immunity is a perfect storm for continued viral spread, and continued morbidity and mortality due to COVID-19, hence the necessity for lockdowns and social isolation to prevent viral spread as much as possible. So, what if there was another way to significantly retard spread of the virus while we wait for a vaccine and herd immunity?

A study just published by University of Cambridge researchers in the Proceedings of the Royal Society A found that widespread mask-wearing can help prevent a resurgence of the virus with less reliance on lockdowns that have proven economically devastating. The study found that if 50 percent or more of the population routinely wore masks, each infected person would on average spread the virus to less than one additional person, reducing the transmission rate by about 75%. That is exactly what herd immunity would hopefully accomplish.

It is important to understand the true value of facemasks. Your typical mask does NOT protect the wearer. Very little of the air a mask wearer breaths is filtered through the fabric. It almost all comes from the sides of the mask and is no different from the air you would breath without a mask. Also, virus in the air can infect through your eyes, which are not protected by a mask. However, masks do a very good job preventing viral laden exhalations, especially from talking and from droplets produced by sneezes and coughs. Thus, the value of masks is in inhibiting spread of virus from infected people, especially from those who do not know they are infected.

A key message from this study to aid the widespread adoption of facemasks would be: ‘my mask protects you, your mask protects me’.