HCQ was tried as a prophylactic by nursing staffs in Vietnam working on Covid wards. That was a study I ran across at Pubmed when I was looking for HCQ tests. They were hoping it might protect them from infection but they were catching covid at the same rate as when they weren’t using HCQ. It wasn’t for lack of trying.
Yes...I don’t think HCQ works for keeping you from getting , but...if you were taking it, I expect you would still catch it (not gonna stop that) but if you have levels built up or start taking it at the onset of symptoms, I expect you would get a less severe case as it knocks down the viral replication to some degree. There is also the interaction with the other drugs that may impact it as well, like zinc.
People who have been pushing IVM or HCQ usually are proposing a cocktail of things, as far as I know.