What is the evidence on wearing masks to stop COVID-19?

Masks are the new gold. Varying recommendations exist surrounding the use of N95 masks – the most popular commodity that has emerged in the face of this pandemic. Though all regions have universally aligned on the need for risk mitigation, the differences between recommendations on use of N95s is subtle but palpable.

While key Western institutions – the Centers for Disease Prevention and Control (CDC), Food and Drug Administration (FDA), and Surgeon General in the US and several other public health agencies in the West – advise against the donning of surgical or N95 masks by the general public, Eastern countries have strongly advocated for their use and have somehow begun to successfully contain the virus. Is there something we are missing?

Why are we not using masks?

Contrary to the Far East, our society has never had a culture of using masks among the general public, and – consistent with this – the stated position of several influential institutions has been that masks are not recommended in protecting the general public from COVID-19. Some have strengthened their position to state that masks are also not effective when used by the general population. One has to reflect on the origins of these recommendations.

A valid argument against the mass use of masks is the notion that they would deplete the resources available for healthcare workers. Many healthcare workers who require masks for adequate levels of personal protection are unable to access them, while they have been hoarded – and effectively weaponized – by fearful consumers and opportunistic merchants.

Masks must first go to our frontline soldiers. However, this does not immediately suggest that masks are ineffective in protecting the general population. These two points have unfortunately been conflated in the court of public opinion. Should we be aiming to best allocate the existing mask volumes to healthcare workers, or should we be aiming to best allocate masks to our healthcare workers and supply the general public? The difference between those two objectives is subtle but material.

Another common argument against widespread use of masks is built upon the acknowledgement that it is costly to furnish several billion people with masks that are disposable. Evidently, mass access to masks will come at a price, however it must first be considered that the alternative – potential economic disaster – is significantly more costly. Furthermore, while single use of masks is justifiable for a healthcare worker, it is not clear that masks cannot be reused by a healthy individual. Even if this individual were asymptomatically infected, masks may offer tremendous benefit in reducing the spread of disease by those without symptoms.

The case for masks

Many regions that have successfully controlled the incidence rate of COVID infections have entrenched cultures of wearing masks, perhaps with the exception of Germany – which had implemented early and meticulous testing protocols to quickly break chains of infection.

China, Japan, Hong-Kong and South Korea all exercised various degrees of austerity in promoting widespread use of masks, particularly for individuals who are likely to engage in interpersonal contact. Notwithstanding that additional strategies have also been implemented – thorough testing, effective contact tracing, mandated social distancing - all of these countries have effectively managed risk.

Areas that have not effectively managed risk, such as New York and Milan, do not have mandated widespread wearing of masks. Though it is currently impossible to conclusively attribute this difference in outcomes to widespread use of masks, we are invited to reconsider its effectiveness as an intervention.

In addition to anecdotal observations, several scientific studies show that masks reduce the risk of respiratory infection in healthcare workers. Meta-analyses showed that "surgical masks or N95 respirators were the most consistent and comprehensive supportive measures” in reducing risk of infection in healthcare workers. Many such studies are observational in nature and, naturally, one would request a randomized controlled trial (RCT) to be the ultimate arbiter of this debate. Fortunately, RCTs on mask usage exist, and one was indeed conducted in 2008 to examine the use of masks in households to prevent respiratory virus transmission. An 80% reduction in contracting respiratory illness among compliant patients was seen. When masks are worn, they are extremely efficacious.

What are we aiming for?

Ultimately, we must reflect on the key global outcome that is being pursued. If we are aiming for the pandemic to run out of steam, the central goal of any intervention should be to bring R0 (the average number of people that are infected by one infected person) below 1, implying that the infection rate no longer grows exponentially.

Masks have a compounding effect in that they both protect an individual from transmitting and being exposed to infection. The impact of this could, conceivably, be a dramatic reduction of R0. If we are to assume masks are 80% effective in preventing spread on an individual basis, the overall risk-reduction in a single interaction between two people should be 96%. If we are to be conservative and assume that low compliance and mask-quality reduce individual risk by 50% instead of 80%, the overall risk reduction within a single interaction between two people is 75%.

If R0 is approximately 4, and we practice existing risk-mitigating strategies such as hand-hygiene and social distancing in addition to wearing masks, it is highly plausible that R0 will be reduced to below 1. Any series of interventions which bring R0 below 1 is the difference between unconstrained growth and eventually stopping the spread of infection. This should be thoroughly considered.

We recognize and support the CDC, WHO and other key institutional leaders that are heroically leading the charge against COVID-19 and invite all stakeholders to acknowledge that – if there is even dubious benefit to the widespread use of masks – consideration is merited. In addition to the general low-risk nature of this intervention, the anecdotal and scientific evidence that surrounds their widespread use is indeed cause for pause, and our thoughts on their utility in this fight should be subjected to objective and sober scrutiny. It could very well be the proverbial little hinge that swings the big door in this fight for humanity.