Copper sulphate is used in veterinary medicine as an antimicrobial spray. Copper metal has been used for centuries as vessels because of its antimicrobial properties, seemingly goods transported in copper vessels stayed fresh much longer.
Copper, however,is a very expensive metal and it would be nigh on impossible to replace every handle in a public place with copper. They probably would get stolen too.
Scientific claims? many:
https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/jam.13681