Neonates i.e. newborns, i.e. up to four weeks old...get neonate herpes, which is life-threatening. Your DB is 9 months old.
The moment the virus takes a hold (indicated by tingling) is when its active and contagious, right through till its still scabby,but should be gone after two weeks, and its possible to get something to cover it.
I have personally never suffered pain with them or used zovirax or any of those things. I tried coffee to start with pointless, but now just use lip balm and they're gone without any pain or itching.
I haven't actually seen any DC with cold sores, and I have certainly kissed mine loads!!
Anyone who's had chicken pox has the virus dormant in their system. So most adults.
The risk for your DB is over.
I have never kissed a baby on the lips?!? My babies have literally tried to climb inside my mouth, as they do at a certain age and you can't keep their fingers out but not contracted the virus. Maybe I have passed on an immunity.
I think you can feel a lot more calm and confident that your DB will not get it OP, because it's too old - no longer a neo-nate.
However you won't be able to stop your DB catching the virus. My family don't have it,so I have no idea where mine came from.