When I was a child and would get
strep throat, my pediatrician would prescribe
antibiotics for my mom and dad too as my germs were so strong, LOL, they still are. It did not hurt them any and they did not get my strep. So, I think it is all up to the individual. Immunity usually develops if you take something for a long period. I would ask your doctor if you are concerned about this however.
Enjoy your trip.