McM.......I have a certain amount of sympathy for your view....however, if that should be the case, then how would we develop antibodies to the offending pathogens? Wouldn't we be a sitting duck for a devastating infection.
In the VD clinic as it used to be called, there was always a ..."suspicion" that the guys who shagged prostitutes on a regular basis developed an immunity, whereas the poor old office clerk out for a night with the boys was egged on to "have a go" never touched a pro. before.....got a dose on his first venture.
No scientific evidence for the above....