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Why are dog medicines dosed by weight but vaccines are one size?

Updated on September 23rd, 2025

Pet's info: Cat | American Shorthair | Male | neutered | 2 years and 9 months old

Why are medicines given to dogs by weight but vaccines are one size for all?

2 Answers

Most Helpful Answer

Jennifer Summerfield, DVM CPDT-KA

Answered By Jennifer Summerfield, DVM CPDT-KA

Veterinarian, Certified Dog Trainer

Published on May 22nd, 2017

This is because the amount of antigen contained in a single vaccine dose is the amount needed to stimulate an immune response - this has nothing to do with an animal's body weight, because a Chihuahua has the same immune system as a Saint Bernard. The appropriate dose is the same for all members of a given species, which is why the dose does not vary based on size :)
Vote Icon1Pet Parents found this answer helpful

Related Answers from Veterinarians

  • Answered By Jennifer Summerfield, DVM CPDT-KA

    Veterinarian, Certified Dog Trainer

    Published on September 27th, 2017

    Hi there! This is because the vaccine dose is based on the amount of antigen needed to stimulate an immune response, which has nothing to do with the size of the animal. Vaccines are very different from drugs, in this respect! :)

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    1Pet Parents found this answer helpful

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