Wearing Face Mask – A Small Step Towards COVID-19 Immunity?

“Universal masking could become a form of “variolation” (inoculation) that would generate immunity, slowing the spread of the virus”. These are new research findings by Dr Monica Gandhi, suggesting that wearing face mask may be the answer to immunity against COVID-19, while we await a vaccine.

As COVID-19 spreads across the world like wildfire, universal face masking has become the great firewall to prevent further transmission. In fact, the novel virus causing COVID-19, SARS-CoV-2, transmits through speech, sneeze and cough droplets from infected person. Hence, current recommendations from WHO and CDC include wearing cloth face coverings with three layers to prevent the spread of disease. Although it is a well known fact that wearing face mask prevent virus transmission but can it help increase immunity against COVID-19?

Higher Viral Load Leads to More Severe Infections

In general, the higher the exposure to viral load, the more severe the infection. During the first week of infection, our body immune system employs more innate (non-specific) defence against the virus. In a way the body is trying to “buy” time for more adaptive and selective immunity such as antibodies to develop.

The downside of the innate immune system defence is that it can be harmful to healthy body cells. In such a scenario, if the viral load is high, not only does it fail to fight off the virus but the immune cells may damage the body. On the other hand, a small inoculum dose may result in asymptomatic or mild cases.

As proof of concept, a Syrian study on hamsters demonstrated that the higher the dose of virus, the more severe the disease symptoms. Comparatively, when healthy hamsters are protected from infected ones using surgical masks, the chance of transmission is nil to minimal. Even if infected, since the inoculum dose is very small, the resulting infections are mostly asymptomatic or very mild.

Photo from The Telegraph

Universal Facial Masking Lowers The Severity of COVID-19

With the implementation of universal face masking, not only did the rate of transmission decrease significantly, asymptomatic cases rise from 20-40%, to up to 80% of infections. This observation supports the theory that wearing face mask decreases the severity of COVID-19 infections.

Similar observations are seen in cruise ship outbreaks. In an Argentinian cruise, where every passenger wore surgical face masks and staff wore N95 masks, about 81% of COVID-19 patients have no symptoms. In comparison, asymptomatic patients are about 20% in earlier ship outbreaks without universal face masking.

Similarly, in two recent outbreaks in U.S. food processing plants, where every factory worker wore face mask everyday, about 95% of infected personnel have no symptoms while the other 5% only experience very mild symptoms.

Overall, death rate due to COVID-19 remains low in countries that enforce population-wide face masking. Even when lockdown ceases, resurgence of COVID-19 still shows relatively low mortality rate.

Wearing Face Mask May Increase Immunity

If wearing face mask can reduce disease severity to a mild or asymptomatic form, this could be the first step towards developing stronger immunity. The effect can mimic that of “variolation”, a method of immunisation. Variolation is the introduction of tiny dose of viral matter to stimulate disease resistance, eg in small pox inoculations.

For this reason, any strategy that exposes people to the virus and yet produces mild or asymptomatic form of COVID-19 has the potential to increase herd immunity. Research studies have also shown that those who recover from mild or asymptomatic COVID-19 have strong and lasting immunity. Reinfection with SARS-CoV-2 is rare, although there are reports of a few cases.

So, if the theory is true, universal face masking can reduce transmission rate and severity of COVID-19, ultimately increasing population-wide immunity against the virus. There is a need for more studies to validate the hypothesis. These would include comparison of the proportion of asymptomatic patients and successful “variolation” rate in places with universal face masking versus those without.

Photo by USAID in Africa from Flickr

Conclusion

New research suggests that universal face masking slows down the spread of COVID-19 and decrease disease severity. This gives our body a chance to generate immunity against the virus through milder and symptomless infection. With more and more people gaining immunity against the virus, we are able to break the chain of transmission. However, we still need more studies to validate the hypothesis before drawing any conclusion on the topic.

References:

1. Hayes G. Face masks could be giving people COVID-19 immunity, researchers suggest [Internet]. Telegraph Media Group Limited. 2020. (Available from: https://www.telegraph.co.uk/global-health/science-and-disease/face-masks-could-giving-people-covid-19-immunity-researchers/; last updated on 2020 Sept 12; last accessed on 2020 Sept 20)

2. Gandhi M, Rutherford GW. Face masking for COVID-19 – potential for “variolation” as we await a vaccine. NEJM. 2020 Sept 8. DOI: 10.1056/NEJMp2026913.

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