As we have reiterated earlier the COVID-19 pandemic is as much a pandemic of viral mis/dis information as of the virus. One of the pieces of mis/ dis information which has been flying around and infecting people is that Face Shields are a good replacement or even better than Face Masks.
At the heart of the controversy lies the question of whether COVID-19 infections are caused by droplets which fall soon after being coughed out or by aerosols which are very small particles That hang around in the air for a much longer time
Let us unpack this argument. Face Shields are made of clear plastic and cover not only the mouth and nose like Face Masks do but also the eyes which are an important port of entry for the virus. Wearing a Face Shield will also prevent the wearer from touching their face very often. It doesn’t cause as much suffocation as Face Masks and can be disinfected, used and reused with ease. Proponents often quote parts of a study “Efficacy of Face Shields Against Cough Aerosol Droplets from a Cough Simulator” published in the Journal of Occupational Medicine in 2014 to prove that a Face Shield is better.
At the heart of the controversy lies the question of whether COVID-19 infections are caused by droplets which fall soon after being coughed out or by aerosols which are very small particles which hang around in the air for a much longer time and do not fall to the ground. This is like a world series play off with the WHO (with UK, Canada and Australia) on the one side and Rest of the World on the other! In the face of clear and persistent evidence to the contrary the WHO has insisted that COVID-19 infections are principally caused by droplets.
The evidence for Airborne route of infection has become so substantial and the frustration with WHO’s stance so widespread that 239 of the world’s top researchers wrote an open letter to WHO in the Journal – Clinical and Infectious Disease (https://academic.oup.com/cid/article/doi/10.1093/cid/ciaa939/5867798?searchresult=1 ), I quote- “ “Most public health organizations, including the WHO, do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings,” the letter states, “Hand-washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people.”
Face Shields are good to be used Along With Face Masks, they are NOT a replacement for Face Masks!
The evidence for Airborne route of transmission is has been established in numerous articles in reputable journals for example “Evidence of Airborne Transmission of the Severe Acute Respiratory Syndrome Virus” in the New England Journal of Medicine (https://www.nejm.org/doi/10.1056/NEJMoa032867) and in the same journal “Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering” (https://www.nejm.org/doi/full/10.1056/NEJMc2007800 ). The mounting evidence has finally compelled the WHO to make this admission: “ Based on the available evidence, including the recent publications mentioned above, WHO continues to recommend droplet and contact precautions for those people caring for COVID-19 patients. WHO continues to recommend airborne precautions for circumstances and settings in which aerosol generating procedures and support treatment are performed, according to risk assessment.13 These recommendations are consistent with other national and international guidelines, including those developed by the European Society of Intensive Care Medicine and Society of Critical Care Medicine and those currently used in Australia, Canada, and United Kingdom.
At the same time, other countries and organizations, including the US Centers for Diseases Control and Prevention and the European Centre for Disease Prevention and Control, recommend airborne precautions for any situation involving the care of COVID-19 patients, and consider the use of medical masks as an acceptable option in case of shortages of respirators (N95, FFP2 or FFP3).”
Coming back to the article which is often quoted partially in the Journal of Occupational Medicine, let us quote it more extensively “We used a coughing patient simulator and a breathing worker simulator to investigate the exposure of health care workers to cough aerosol droplets, and to examine the efficacy of face shields in reducing this exposure. Our results showed that 0.9% of the initial burst of aerosol from a cough can be inhaled by a worker 46 cm (18 inches) from the patient. During testing of an influenza-laden cough aerosol with a volume median diameter (VMD) of 8.5 μm, wearing a face shield reduced the inhalational exposure of the worker by 96% in the period immediately after a cough. The face shield also reduced the surface contamination of a respirator by 97%. When a smaller cough aerosol was used (VMD = 3.4 μm), the face shield was less effective, blocking only 68% of the cough and 76% of the surface contamination. In the period from 1 to 30 minutes after a cough, during which the aerosol had dispersed throughout the room and larger particles had settled, the face shield reduced aerosol inhalation by only 23%. Increasing the distance between the patient and worker to 183 cm (72 inches) reduced the exposure to influenza that occurred immediately after a cough by 92%. Our results show that health care workers can inhale infectious airborne particles while treating a coughing patient. Face shields can substantially reduce the short-term exposure of health care workers to large infectious aerosol particles, but smaller particles can remain airborne longer and flow around the face shield more easily to be inhaled. Thus, face shields provide a useful adjunct to respiratory protection for workers caring for patients with respiratory infections. However, they cannot be used as a substitute for respiratory protection when it is needed.” Face Shields are good to be used Along With Face Masks, they are NOT a replacement for Face Masks!