Effectiveness of face shields for COVID-19 protection

Editor's Note

This study led by researchers in the UK finds that face shields do not give high levels of protection against external droplet contamination.

The researchers compared 13 styles of face shields in controlled laboratory settings, using a “coughing machine” that ejected fluorescent drops onto manikin heads.

Among the findings:

• None of the face shields totally eliminated exposure.
• Face shields that were more open at the head band led to breaches when the head was tilted forward.
• Face shields with a shorter visor led to breaches when the head was tilted back.
• There were more breaches, or breaches with a higher concentration, on large heads vs small heads, probably because of less coverage at the periphery of the face.
• The large gaps around many face shields provided opportunities for droplet ingress.
• Face shields with complete wrap around facial coverage were more protective, stable on the head, and easier to wear correctly.

Early in the COVID-19 pandemic, some argued that face shields offered a high degree of protection, were comfortable, and did not hinder communication. However, the researchers say they could not confirm that face shields consistently offered high protection to wearers. They added that their findings show why both laboratory and real-world evidence are needed in assessing the utility of any personal protective equipment.