We’ve been dealing with a major shortage of canine influenza vaccine for a while. That’s caused a few different hassles, some related to disease and others related to vaccination requirements.

A quick recap: There are a couple of different strains of dog-adpated flu internationally, but currently we’re really just worried about H3N2. This strain is present in Asia and the US (to which it was imported from Asia). It was introduced to Canada (specifically Ontario) a couple of times in 2018, but we were able to contain it and I’m not aware of any spread of it up here since then, but we remain on the lookout.

From an epidemiological standpoint, canine flu is different from human flu in that it’s not particularly seasonal, and it’s not as widely distributed. In the US, we see sproradic cases and outbreaks that seem to jump around the country (likely related to dog movement), often causing local outbreaks that tend to burn out. In contrast, human (seasonal) flu is more widely disseminated and most people are at some risk of exposure. Currently most dogs probably have little chance of encountering canine flu, but we have a hard time predicting which dogs will get exposed, since the virus jumps around geographically.

Canine flu vaccines are, well, just like other flu vaccines, in that they’re reasonably good at what they’re designed to do: reduce the likelihood and severity of disease. They’re not meant to stop the spread of the virus altogether, or contain an outbreak. They’re used to reduce severe impacts on dogs that get infected.

There are two main groups I think about in terms of dogs that benefit from canine flu vaccines:

  1. Dogs that are at increased risk of exposure to flu. Those include dogs that have contact with lots of other dogs, dogs that travel to areas where flu is spreading and dogs that have contact with dogs imported from high risk areas (e.g. Asia).
  1. Dogs that are at greater risk of severe disease or death if they get infected. Unfortunately this group is often overlooked. Older dogs are the main concern, since flu deaths tend to occur mostly in senior dogs. However, it also includes the very young, pregnant, immunocompromised, brachycephalic breeds (smushy faced breeds like bulldogs) and dogs with underlying severe heart or lung disease.

The first group is more likely to be exposed but the second group is more likely to be seriously impacted. So, if push comes to shove, I want to focus on vaccinating that second group. That protects more dogs from serious disease and doesn’t negatively impact control much (if at all), since flu vaccines are not a good tool to prevent transmission in the first place.

However, if we look at what dogs actually get vaccinated, it’s often dogs in low risk areas that go to kennels or group events. It’s not necessarily because of a high risk of exposure to flu or a high risk of complications, it’s because someone has made it part of admission requirements.

What’s the benefit of requiring flu vaccination for boarding or day care?

  • The benefits are pretty limited, from a facility standpoint. It might help reduce transmission if an infected dog gets in, but that’s probably marginal. Flu is really transmissible, so I doubt even having good flu vaccine coverage in a group of dogs will really prevent an outbreak. It will reduce the degree of illness in individual dogs, but not do a lot to protect the facility (and that’s the premise for requiring vaccination).

That means by vaccinating all these dogs, we’re burning through our limited vaccine supply for very limited gain. In a time of shortage, I’d rather see vaccine diverted to situations where it is more likely to have an impact:

  • Dogs at higher risk of serious disease
  • Situations where vaccination is needed for dog movement (e.g. someone moving to a country that requires flu vaccination of dogs prior to importation)

Would I like all dogs vaccinated against the flu? Sure. It’s not going to happen, though. So, while we’re in a period of vaccine shortage, here’s how I’d prioritize our limited supply: