Puppy Vaccine Timing

Congratulations, you’ve adopted a new puppy or kitten! You’re probably looking forward to introducing your new “baby” to your home, to your family or roommates, and to the other pets in your household. You can’t wait to buy them all sorts of toys to play with, a collar with a custom tag just their own, and a cozy pet bed they’ll love to snuggle up in.

I’m guessing you might NOT be so excited about taking them to the veterinarian two, or three, or maybe even four times over the next few months to get all their puppy or kitten vaccines. But that’s exactly what I want to talk about today…

Why does my puppy or kitten need SO MANY vaccinations??

There are a few reasons behind this, so let’s take them one at a time.


Your puppy or kitten’s immune system isn’t done developing. Newborn puppies and kittens can’t yet walk; they can’t see, as their eyes aren’t open yet. Many other internal systems are still developing as well, including their immune system. On average, most puppies reach immunocompetence, or an immune system that is sufficiently developed to respond to environmental threats, by 6-12 weeks, some as much as 16 weeks. We are not able to predict when an individual puppy or kitten will reach that point, so veterinarians have to play it safe and assume that we need to provide external protection until 12-16 weeks of age.


Maternal antibodies that were passed on through nursing can interfere with vaccinations. The transfer of maternal antibodies is called Passive Transfer of Immunity, and it generally occurs in the first 24 hours of life. These antibodies can bind to the antigens in the vaccine and effectively “hide” it from the puppy’s immune system, thus preventing them from mounting a strong immune response of their own. How long do these maternal antibodies stick around? For example, maternal antibodies to Canine Distemper and Canine Parvovirus have been shown to reach insignificant levels at approximately 10-12 weeks, and 15 weeks, respectively. This is another good reason to continue providing intermittent vaccinations until your puppy or kitten is at least 16 weeks old.


Multiple vaccine boosters increase the immune system response in most cases. A good way to think about this is that the first injection of a vaccine primes the immune system, and the subsequent doses of that same vaccine serve to amplify the immune response and provide a much stronger level of protection in the future. If only a single dose is given, many times this is not enough to provide robust, long-lasting protection against illness.


It is recommended that vaccination sessions be given 2-4 weeks apart. If you give vaccines less than 2 weeks apart, it’s possible that the immune system response instigated by the first set will neutralize the second vaccinations before they are ever “seen” by the immune system cells. But if you wait longer than 4 weeks, it’s possible that the immune system cells may have “forgotten” the initial vaccination and you’d essentially be starting from scratch again.

To learn more about recommended vaccinations and vaccine timing, this article written by a veterinarian is a great place to start: Vaccine info.


  1. Callahan, G.N., & Yates, R.M. Basic Veterinary Immunology. University Press of Colorado, 2014.
  2. Pereira, M., Valerio-Bolas, A., Saraiva-Marques, C., Alexandre-Pires, G., Pereira da Fonseca, I., * Santos-Gomes, G. Development of Dog Immune System: From in Utero to Elderly. Veterinary Sciences, 6(4), Oct 2019, 83; Pereira et al.

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