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Dog vacinations
An_251629 posted:
If a dog is vacinated with a three year vacination, after a four year period of not being vacinated, does the dog need to be vacinated again before the three years are up
srstephanie responded:
Hi An_251629,

If you are talking about the core vaccines: Distemper, Adenovirus, Parvovirus ... then, no, you do not need to revaccinate prior to the three year period. All of those vaccines are Modified Live Virus vaccines (MLV) and a single dose to an adult dog, even if never vaccinated before, will produce protective immunity (i.e. for most dogs, there are always a few dogs that are "non-responders" and there is never a 100% guarantee of protection with any vaccine).

With Rabies, future boosters are determined by what the vaccine is licensed for ... and state/local legal requirements. Most states and municipalities accept what the rabies vaccine is labeled for. So, if using a "1-year" vaccine, then you would need to booster in a year. If using a 3-year rabies vaccine, then you don't need to booster before three years.

One question may be what the dog's previous vaccination history was and how old at the last vaccine (4 years ago). Was the dog an adult four years ago ... or was that just part of the puppy series? It is generally recommended that after the puppy series (for which the last vaccination should be given at 14-16 weeks of age), all the core vaccines should be boostered "no later than" 1 year after the last puppy series ... THEN you can go to a three-year booster protocol. The experts like to have that first booster once the dog becomes an adult (with a fully mature immune system) to get a good response, and then go to the longer booster intervals.

If your dog didn't have that first booster, no later than 1 year after the last puppy series ... and it has been four years since the initial puppy series ... then some vets might want to give a two dose series now. Immunologically, it isn't necessary, but some (many) vets may feel more confident with a two dose series (given at least 2 weeks apart and before 6 weeks). For adult dogs that have never been vaccinated before ... most vets will give a two dose series, even though immunologically, one dose of the core vaccines is all that is needed since they are all MLV vaccines.

But if the dog has been previously vaccinated, particularly if that last vaccination was as an adult ... then, no matter how many years go by before the next booster, only a single vaccination is needed and you can wait at least three years for another booster.

In reality, once vaccinated as an adult with the core vaccines, immunologists feel that most dogs are immune for life, particularly for parvovirus. Many vaccine manufacturers have "duration of immunity" studies that show protection for "at least" 5-7 years. But vets and the experts still tend to recommend boosters every 3 years just to protect the occasional dog that may not have responded well to a previous vaccination.

The one exception is always Rabies ... for which you must follow local legal requirements ... most of which follow whatever the rabies vaccine is "labeled" for ... either 1-year or 3-years.

My info comes from the 2011 AAHA Canine Vaccination Guidelines (

I also highly recommend an article on Overdue Vaccinations by Dr Richard Ford (a co-author of the AAHA Guidelines) in the Nov/Dec issue of Today's Veterinary Practice. Much of my above info came from it. I admit my bias, he is a good friend of mine and my mentor, but he is also considered a vaccine guru by his peers and highly respected as one of the top experts on vaccination protocols. Here is a link to his article on overdue vaccinations (one of an on-going series on vaccination questions)

Hope that helps.

Stephanie in Montreal (soon to be Raleigh, NC)


Sandy Willis, DVM, DACVIM, is a small animal internal medicine consultant for Phoenix Central Laboratory, an independent veterinary diagnostic laborat...More

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