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The protective measures in the new normal work

Should we add face shields?

Our new normal has become social distancing and wearing a face mask. Many people are disregarding the advice and are moving back to life as it was before. But if the protective measures really work, we shouldn’t lower our guard yet. I have the answer for you.

Social distancing and face masks are effective

A recent study published in the Lancet on June 1st says they work. It is a meta-analysis, but is the best study so far in the absence of randomized clinical trials.  Chu and colleagues included in their analysis the results of 44 comparative observational studies from 16 different countries across 6 continents. They reviewed the effect of physical distance, face masks (surgical masks, N95 respirators, etc.), and eye protection on transmission of SARS-CoV-2 (COVID 19), SARS-CoV (Severe Acute Respiratory Syndrome) and MERS-CoV (Middle East Respiratory Syndrome).

The authors showed a reduction in risk of 82% with a physical distance of 1 m for both health­care and community settings. Every additional 1 m of separation more than doubled the relative protection.  They also reported that face masks and respirator masks reduced the risk of infection by 85%. Respirators masks -used by health care workers- were 96% effective and other masks were 77% effective. Eye protection resulted in a 78% reduction in infection which might occur by aerosol transmission or touching the eyes with infected hands. They also mentioned that multilayer masks are more protective than are single layer masks. This is of interest since most home­made cloth masks are single layered. A well-designed cloth mask should have water-resistant fabric, multiple layers, and good facial fit. 

Medical face masks which offer the best protection come from China and because of closing of some factories and an increased worldwide demand they are in critical shortage. To circumvent this, the Center for Disease Control and Prevention recommended that members of the community use cloth masks –even though they are less effective- so there is more availability of medical masks for health care workers.

Face shields, a viable alternative

An alternative could be the use of face shields which are clear plastic or plexiglass shields that cover the entire face, from the forehead down to the chin or lower and have an elastic headband to hold the shield in place.

We don’t have any studies evaluating their effectiveness in preventing COVID-19 but they appear to significantly reduce the amount of inhalation exposure to the influenza virus. A simulation study from a few years ago showed a 96% decrease in contamination of a person from the influenza virus when droplets are coming at them when a face shield has been used at about 18 inches. This protection could be further increased if the source was also wearing a face shield and not only the person at the receiver end. This can also work for the SARS-CoV-2 virus, since its mode of transmission seems no different from other respiratory viruses. We get infected through infectious droplets contaminating directly eyes, nose or mouth or by touching a contaminated surface with those droplets and then touching one’s eyes, nose or mouth.

Shields may have a number of advantages over masks. They can be cleaned with soap and water or common disinfectants and reused. Have you tried them? They are more comfortable to wear than masks and it is easier to breathe through than through a mask.

You probably touched your face when trying to adjust the mask. If your hands were contaminated, and you inadvertently touched your eyes, mouth or nose, you could have given yourself the virus. You probably also tried to scratch your face when itching. Well, the shield forms a barrier that keeps you from easily touching your own face. Shields seem to facilitate communication better than a mask. I am sure you have seen that people often pull down the mask when speaking; well, there is no need to remove the shield when talking. You can also see the facial expression and the movement of the lips which helps your understand the other person better.  

Because they extend from the forehead, shields offer protection to the eyes as well as nose and mouth. They work differently from a mask. While you wear the mask mainly to protect others around you, the shield offers you more protection from the people around you. Since the shield is away from your face, if you cough, droplets can still get out and contaminate others. A potential drawback is that they need to be cleaned thoroughly because the shield provides a surface –plastic- where the virus can survive.  

Shields have been successful in hospital settings -doctors tend to use both mask and shield for protection- and they should also work well in a community setting. Studies to confirm their effectiveness are needed. In the meantime, considering that availability of masks is limited, and shields can be easily produced and distributed locally, they should be incorporated as part of our protective measures as we relax social distancing moving forward.

Conclusion

No one intervention is completely protective, and combinations of physical distancing, face masks, face shields, and hand washing are needed to mitigate the COVID­19 pandemic until we have an effective vaccine.  

References

Chu DK, Akl EA, Duda S, et al. Physical distancing, face masks, and eye protection to prevent person­to­person transmission of SARS­CoV­2 and COVID­19: a systematic review and meta­analysis. Lancet 2020; published online June 1. https://doi.org/10.1016/S0140­6736(20)31142­9. 

Eli N. Perencevich, MD, MS; Daniel J. Diekema, MD, MS; Michael B. Edmond, MD, MPH, MPA. Moving Personal Protective Equipment Into the Community. Face Shields and Containment of COVID-19. JAMA. 2020;323(22):2252-2253. doi:10.1001/jama.2020.7477

LindsleyWG, Noti JD, Blachere FM, Szalajda JV, Beezhold DH. Efficacy of face shields against cough aerosol droplets from a cough simulator. J Occup Environ Hyg. 2014;11(8):509-518.

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