Do Small Dogs Need a Smaller Vaccine Dose (+ is it safer?)

Why is it that the vaccine dose is the same for small breed dogs and giant breed dogs?

Every other medication is dosed based on size, so shouldn’t that make a smaller vaccine dose safer in small dogs?

do small dogs need a smaller vaccine dose?

A week ago our 3 pound 4 ounce Chihuahua received her first Lyme vaccine. She has a slight rash on her belly and two red spots by her pee-pee. She just turned one year old. Do you think she was too small for this vaccine? Now I’ m worried - Christine

Is Vaccination Needed?

Let's start by saying that in general, vaccine reactions like this are very uncommon. While she is very small, in my mind that would never be a reason not to vaccinate. Vaccines do prevent potentially fatal disease.

In this case, the question is about Lyme disease. Lyme disease, Leptospirosis and Kennel cough are all examples of non-core vaccines which are only administered after a risk assessment. That is based on the risk of disease in your local area and the lifestyle of each individual dog.

Lyme disease is transmitted by tick bites. If you are living in an area with Lyme disease present and with a high tick presence as well, then the vaccine is certainly something to seriously consider. Unfortunately, Lyme disease is becoming more and more prevalent with global warming. The disease, as well as ticks, are spreading to parts of the world that never used to have this problem before.

Smaller Vaccine Dose

The next question is, should small dogs get a smaller vaccine dose than large dogs?

Small dogs are slightly more likely to develop vaccine reactions. However, these reactions are only expected in less than four out of every hundred dogs. That’s less than 4% of dogs. As well, in the vast majority of cases, a vaccine reaction is nothing more than being just a little quiet and a little off food for 24 to 48 hours. Nothing more serious than that happens and no treatment is needed.

More severe reactions are possible, but they are thankfully very rare. I've never seen a dog or a cat have an anaphylactic allergic reaction to a vaccine. It's a potential possibility. I'm sure it does happen, but it is really very rare.

So where does vaccine dose come into this?

Well, we know that the full vaccine dose is generally very safe and also produces a reliable immunity.

When it comes to safety, this has clearly been shown in numerous studies. A consideration when it comes to discussing small and toy breed dogs is that these studies will not necessarily check every single breed or every single size of dog.

Is a smaller vaccine dose safer

We don't know that for certain, but it would make sense that a smaller vaccine dose in small breed dogs, like a really tiny Chihuahua, is probably going to result in fewer side effects.

However, we also have no idea if this smaller dose would produce a reliable protective immunity in every dog from the killer diseases that they are designed to protect against. So, on the one hand, there may be fewer side effects, but the vaccine safety is actually worse because a “vaccinated” dog could still contract a potentially fatal disease like Parvovirus.

This isn't something that we want to mess around with. There's absolutely no point in vaccinating at all if we don't know that we are going to get that reliable protective immunity that is been proven to be the case with the dose of vaccine given.

small dogs are slightly more likely to develop vaccine reactions. However, these reactions are only expected in less than 4 out of every 100 dogs

Small Breed Testing

In an ideal world, there would be lots of tests that go into small dogs. It may be that we will be able to produce a smaller dose vaccine in the future that proves just as effective, but just to take that into our own hands and, for example, administer half a dose will potentially leave your dog open to contracting one of these killer infections.

Vaccine Reactions

If we are talking about vaccine reactions in general and side effects, then in Christine's dog I'd say I would expect a skin reaction to happen really within a day or two. Normally that would be a local reaction, like a little lump that forms where the vaccine was given, that then disappears over a week or two. It is nothing more serious than that.

The other type of skin reaction to vaccines are a result of an allergic reaction. If allergic reaction or anaphylactic reaction develops, then it generally starts within minutes to a few hours of a vaccine being given.

You can see that when we get vaccines ourselves and for our children. We are advised to stay at the doctor’s surgery for 20 to 30 minutes after receiving the vaccine, just in case there is an allergy develops.

For dog’s that do suffer from a vaccine allergy, hives would be the most typical. This manifests as lumpy, bumpy skin that can be quite itchy. Dogs can also get swelling of the face and neck, start vomiting, have diarrhea, experience labored breathing, and even collapse. A severe anaphylactic reaction can even be fatal.

That said, a rash is clearly not normal in this wee dog.

It would definitely be worth calling your vet if it is itchy, getting worse, or persisting. Skin rashes and lesions can only be properly diagnosed with a hands-on examination, along with some simple tests depending on the individual case.

Vaccine Alternatives

Finally, let's briefly move on to prevention of Lyme disease.

I mentioned that vaccination is only one part of disease control, and it may not be appropriate for every dog, even if Lyme disease is in your area. Reducing tick exposure and appropriate tick control is really a very important addition to and prevention plan, and is especially important in dogs who are not vaccinated. 

If you live in a Lyme area, you can check out my article all about Lyme disease and tick control for the other steps you should strongly consider implementing.

The above is a transcript taken from “The Dr Alex Answers Show”.

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