I am exporting my dog from Spain to Hong Kong in September.

As far as I know, to Hong Kong, he had to stay in quarantine for two weeks outside. The flight from Spain may be very hard on him too. All the vaccinations are kept up to date it remains current. According to hong kong law, he does have to get the rabies injection every three years even he has a certificate proving that the antibody level from the vaccination is high enough. You must have this done six months before you travel.