I hear people all the time say, hey the masks kept me from getting the flu or even a cold this year. Does seem to keep minor ailments away.
It’s not the masks. It’s a well known phenomenon called Viral Intererence.
Viral interference is a state of temporary immunity, is a state whereby infection with a virus limits replication or production of a second infecting virus.
I think one of the reasons people didn’t get as many colds and flus this year had less to do with the masks and much more to do with the kids being mostly remote in schools, the extra sanitizing, esp. in schools, and the fact that people stayed home or went out much less and really did try to stay away from folks.