The World Health Organization [WHO] said in the update that face shields cannot replace mask-wearing and other safety guidelines of social distancing.

The devices do not block respiratory droplets, making them an inferior alternative when masks can’t be worn either due to availability or difficulty. Fox News reported

The most recent clinical studies organized by UCLA confirmed that a face shield alone will only reduce airborne particles by about 4%, KTLA reported.

“This is likely because the face shield does not fit the face snugly, and thus, cough droplets can escape from the open gaps around the shield,” researchers said, according to KTLA.

The Associated Press [AP] had previously reported that health officials don’t recommend the shields as a replacement for masks but said they could be used in conjunction with a face mask, to help protect eyes and giving a physical barrier to block wearers from touching their face.

The WHO also advised the public to wear a non-medical grade mask inside where physical distancing of a meter — or about 3 feet — can’t be maintained, CTV reported. The group reminded that masks with valves should not be used, and masks should not be worn during vigorous physical activity.