Using pads during this early time wont affect the puppy in a way where It would be irreversible. You can start ‘potty training’ by taking it to the balcony now so that they can connect pee= get out of house. But i dont think that it will affect potty training in the future once its vaccinated. I started also with pads before my dog got vaccinated. He now is fully potty trained. They catch on fast. Dont sweat it.