Face Masks and COVID-19: What are the scientific facts?
From the start of the COVID pandemic, authorities throughout the world have recommended wearing a face mask, practicing frequent and thorough hand hygiene, and social distancing as the most effective precautions to both protect ourselves and help slow the spread of this deadly disease. Yet the issue of wearing a face mask is- if anything- becoming more controversial among the population and a recent report states that 80% of respondents who wear face masks still have questions about it. So what are the facts? Here is scientifically resourced information from a number of clinical trials, in the United States as well as throughout the world.
First let’s talk about the different kinds of face masks.
The “gold standard” in face masks are N95 masks. N95 masks are actually a type of respirator that filters out both large and small inhaled particles. The name derives from these masks block 95% of very small airborne particles. Healthcare workers are trained specifically in the fit and use of these masks in the workplace. Because of a general shortage of these masks, the recommendation for the general population is to instead rely on disposable masks or cloth face masks.
The disposable, usually blue face masks are called surgical masks. These loose fitting masks when worn correctly protect the wearer’s nose and mouth from contact with any droplets/particles or sprays that contain germs, including the virus. Surgical masks also protect others by reducing exposure through air or saliva coming from the wearer.
Although these masks are not specifically approved for healthcare workers, they provide some protection in these settings when N95 masks are not available.
Cloth face masks are designed to trap droplets that are released when the wearer talks, coughs, or sneezes. If everyone wears a cloth face mask, it will reduce the spread of the virus from individuals who are infectious but don’t know it. Cloth face masks are most likely to reduce the spread when worn in any public setting and that protection is enhanced by social distancing and hand hygiene. Cloth face masks can be made of a wide variety of materials, with varying numbers of layers.
Unacceptable face masks: Some N95 respirators, as well as some cloth face masks, have one-way valves that can make them easier to breathe through. Although these masks can protect the wearer from coming into contact with the virus, they DO NOT protect others if the wearer is infectious since unfiltered air is expelled. That is why these masks are actually banned in many places for community use.
What do the scientific studies tell us about the efficacy of face masks in absorbing- and not transmitting- the coronavirus and other respiratory particles? In the past 6 months there have been thousands of studies asking this question with a wide variation in the scientific value of the studies. The best way to assess what information is reliable is something called a meta-analysis. Meta-analyses are statistical studies the include a large number of studies asking the same question. The value of meta-analyses are the strict objective inclusion/exclusion criteria to eliminate out the unreliable studies. A review of two such analyses provides very clear evidence of when the use of facemasks are effective in community settings – what applies to all of us. The conclusions of both of these analyses are that proper wearing and use of face masks in the community setting are effective at slowing the spread of this virus, especially as infected persons in the community do not show symptoms. The type of cloth in the face mask does make a difference in how well it absorbs virus particles. Single layer cloth face masks, including scarves, are somewhat protective but less than double layered masks especially with an additional filter. Surgical masks – the disposable blue ones – are 3 times as protective as a single layer cloth mask but are comparable to layered cloth masks with filters. Additionally, it was reported that face mask usage was even more effective with hand washing and careful hygiene. Some studies compared partial coverage vs high coverage. We all have seen individuals wearing masks – sort of – but usually below the nose. Most studies report that partial coverage is more effective than no mask but only roughly 25% as effective as a full coverage – covering nose and mouth- mask.
The bottom line – supported by numerous studies of community spread in a number of countries including the US- is that wearing a mask in public is effective at slowing/reducing the spread of COVID. It is important to wear the mask correctly – make sure the mask covers your nose and mouth; don’t touch your mask with your hands; when you remove the mask- wash your hands – carefully remove the mask by the ear loops and put it in the wash. Wash your hands again.