
Before the pet travel scheme there was no problem having a 7 week old pup vaccinated.
I think the 12 week thing is to avoid maternal antibody interference where the dam would have been vaccinated against rabies as is routinely required in many countries.
I was told there was no issue with doing it earlier if the pups dam had not been vaccinated against Rabies.
The pup done at 7 weeks was 12 years ago.
There is no requirement for a pup under 12 weeks going to USA to have Rabies vaccination, I exported one in 2005 at 9 weeks old.
In fact we imported a pip at 9 1/2 weeks in 2002 who was Rabies vaccinated as part of the Quarantine rules.