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Puppies are very susceptible to parvovirus and you are right to be very concerned.
I cannot stress this enough, the BEST source of information about how to care for an animal is NOT the breeder, it is a veterinarian. There is no evidence that vaccinating dwarf siberian huskies cannot be done before 6 months. I'm not sure where the breeder got this idea, it may just be their own opinion. Remember that veterinarians have completed a 4 year college degree, as well as 4 years in veterinary college, and passed a stringent certifying examination in order to qualify to give you advice.
When you get your pup, you need to take him to your veterinarian right away and have a thorough physical examination done to make sure you are getting a puppy in good condition. Your vet will listen for heart murmurs, may check a stool sample, in the ears, eyes and so on.
You should continue feeding whatever the puppy has been eating for a week or so while he settles in to his new home, then make a gradual switch over about a week, to whatever good puppy food your vet recommends. I advise following whatever vaccination schedule your veterinarian recommends for the area you live in. Avoid taking the pup to any dog parks, or mingling with dogs other than yours until he has had all his vaccinations.
Best wishes for you and your new little friend.