I’ll start this off with an introduction to Ozzie, our new-ish pup (he got introduced on Twitter earlier but I haven’t used him for blog material yet).  We got him at 7 weeks of age, a day after he was vaccinated, and we need a vaccination plan going forward. It’s ultimately pretty simple, but it’s worth going over some of the common issues.

Yesterday’s post talked about when we vaccinate young animals against rabies. Today I’ll write about the other “core” vaccines. These other species-specific core vaccines are recommended for all dogs or cats, and are typically combined into a single injection containing multiple modified live viruses – viruses that are still alive and induce a nice immune response but are attenuated so they shouldn’t cause disease. For dogs, core vaccines include those for canine parvovirus, distemper virus and adenovirus (with parainfluenza tagging along). For cats, it’s feline herpesvirus, calicivirus and panleukopenia virus. These can be devastating diseases and we want all dogs and cats vaccinated against them, and we want them protected as early in life as possible. Fortunately, these modified live vaccines are really effective and can provide protection even with a single dose – under the right circumstances.

These core vaccinations can be started as early as 4 weeks of age in dogs and 6 weeks of age in cats, but most often pets are vaccinated at 8, 12 and 16 weeks, +/- another shot at 20 weeks. That’s often interpreted as “we need to make sure they get a series of doses spaced out monthly for the vaccine to work.” For some vaccines, we need an initial priming dose and then a properly time booster. However, that’s not the case with these modified live vaccines.  In reality, the reason for the series is “we need to vaccinate them until we’re sure they’re old enough to respond properly to the vaccine.”  Here’s why:

  • Puppies and kittens get antibodies from their mothers. Most often, that will include antibodies against these core diseases. That’s good for protection for when they’re very young, but those antibodies can also inhibit vaccines.
  • We vaccinate young animals knowing those initial doses might not work.  If they do, great, and we’ve helped protect the pet at a young age. If not, we vaccinate again later. We keep doing that until we hit an age where we can be confident that antibodies from mom have waned enough that the vaccine will work and will stimulate the puppy or kitten’s own immune system.
  • Once they hit 16 weeks, we’re pretty confident about that. So, we want to make sure they get a dose at 16+ weeks. If it’s a higher risk situation (e.g. shelter, dog that will be exposed to lots of other dogs), then another dose at 20 weeks provides an extra level of assurance. It may not be needed, but it’s a good backup plan.

So, it’s not that we need to give puppies and kittens lots of vaccines, with an initial shot and then a series of boosters to get adequate immunity. A single dose of these vaccines at the right time will do it. It’s a matter of needing a dose to work at some point, but trying to protect that animal as best we can during that uncertain period before then.

Is that just a matter of semantics? Does it matter if we’re giving series because of timing or a need for multiple doses?

  • Under normal circumstances, no.
  • Where it becomes in issue is when we get off schedule (e.g. missed dose), when we start late (e.g. don’t see the animal until 16 weeks of age) or when we’re starting with an adult (e.g. imported dog, dog with no known vaccination history).

In those situations, we don’t necessarily need a 3 or 4 dose vaccine series, and we don’t need to try to squeeze young animals back into an 8/12/16/20 week schedule. We just need to get one or two doses of vaccine into them at a time when the vaccine will work.

Here are some examples of how core vaccination of a dog can be adjusted:

Adult dog with no vaccine history

  • One dose will probably be fine, but a second dose is often recommended to provide additional assurance of protection.

Puppy that starts its vaccination series late

  • Missed earlier doses don’t matter. If the animal comes it for the first time at 12 weeks, it gets the 12 week (plus a rabies vaccine!), then 16 week +/- 20 week dose. There’s no need to “catch up” on that 8 week dose. It was simply a missed opportunity and we move on.

Puppy that misses a dose in its vaccination series

  • If the dog was vaccinated at 8 weeks of age, and it doesn’t come back until 16 weeks, the 12 week dose is just ignored. It would get its 16 week dose (plus a rabies vaccine!) and then likely a 20 week dose. We don’t care about the time between doses (unlike some of our killed vaccines, where we want a properly spaced initial series.

Back to Ozzie. He was vaccinated at 7 weeks. Does that mean he still needs an 8 week dose? Does he get his next dose at 12 weeks or is that too long?

  • His 7 week vaccine was to try to get him early protection. I’ll vaccinate him next at 11-12 weeks. I’m not hung up on a month spacing so it will be somewhere in that vicinity. He’s a pretty low risk dog given where we live and his encounters with other dogs, but I want to make sure he’s protected.
  • After his 11-12 week dose, he’ll get one at 15-16 weeks. If I was going to stop at that dose, I’d make sure it was at 16+ weeks. However, I will probably err on the side of caution and give him a 20ish week dose so it doesn’t matter if this dose is at 15 or 16 weeks. After his ~20 week dose, he’s done until next year.

The key points:

  • Start vaccinating puppies and kittens early to protect them from these devastating diseases.
  • Make sure they get one or more doses at an older age where we’re confident the vaccine will work.

Next up on the blog: some vaccine dogmas that don’t have any foundation. Stay tuned.