There was an outbreak of "several" coronavirus cases at a hotel among staff and guests in Switzerland.
Health officials found that only people who wore plastic face shields were infected.
The WHO and other authorities have advised that face shields can offer an added layer of protection, but in addition to a mask, social distancing, and handwashing, not as a substitute.
A health department in Switzerland is now warning against wearing plastic face shields without a mask after a recent outbreak in which those wearing only shields were infected with coronavirus, while people wearing masks were fine.
Local health officials determined that all those infected had been wearing only plastic face shields as protection.
Local health officials told the Swiss news outlet 20 Minutes that the face shields could create a false sense of security, leading wearers to take unnecessary risks or lapse in other precautions.
The WHO supports face shields as a tool to curb coronavirus spread, but warns that no face covering will stop the virus entirely. »