Kar Keung Cheng, Tai Hing Lam, Chi Chiu Leung
Published: April 16, 2020
Mass masking is underpinned by basic public health principles that might not have been adequately appreciated by authorities or the public. First, controlling harms at source (masking) is at least as important as mitigation (handwashing). The population benefits of mass masking can also be conceptualised as a so-called prevention paradox—ie, interventions that bring moderate benefits to individuals but have large population benefits. Seatbelt wearing is one such example. Additionally, use of masks in the community will only bring meaningful reduction of the effective reproduction number if masks are worn by most people—akin to herd immunity after vaccination. Finally, masking can be compared to safe driving: other road users and pedestrians benefit from safe driving and if all drive carefully, the risk of road traffic crashes is reduced.
Social distancing and handwashing are of prime importance in the current lockdown. We suggest mask wearing would complement these measures by controlling the harm at source. Mass masking would be of particular importance for the protection of essential workers who cannot stay at home. As people return to work, mass masking might help to reduce a likely increase in transmission. South Korea and Hong Kong have managed to limit their COVID-19 outbreaks without lockdown. It is difficult to apportion the contribution of various measures, including extensive testing, rigorous contact tracing, and strict isolation, but use of masks in public is universally practised in these two places. We encourage consideration of mass masking during the coming phases of the COVID-19 pandemic, which are expected to occur in the absence of an effective COVID-19 vaccine. Finally, this practice could also be useful for control of future influenza epidemics.
The Lancet – DOI: https://doi.org/10.1016/S0140-6736(20)30918-1