According to the Baton Rouge General, from a Mayo Clinic Care Network research suggests that the coronavirus usually spreads via large droplets expelled out of a person’s mouth or nose, which are pulled down by gravity within a radius of six feet. Hence the six-foot rule. They continue by saying that face masks absorb droplets when we sneeze or cough, but face shields do not.
The clinic also suggest that people waring a face shield should sanitize a shield frequently. Disinfecting it with an antibacterial wipe, alcohol, or simply with soap and water.
Full article: BRGeneral.org