How Flu Vaccines Work for Dogs

Published Feb. 7, 2013

If you’ve been paying attention to the news at all over the last few weeks, you’ve been hearing about the 2012-2013 flu epidemic in people. Invariably, any discussion of the flu includes comments regarding the effectiveness or lack thereof of the flu vaccine.

I thought this topic was worthy of discussion here, because owners need to understand what flu vaccines can and cannot do in order to decide whether or not their dogs should be vaccinated against canine flu.

First a couple of facts. The type of flu virus that typically infects dogs (H3N8) is very different from those which infect people (influenza B viruses, H1N1 viruses, and H3N2 viruses). Barring a pretty major reshuffling of the viruses’ genomes, the chance of catching flu from your dog or your dog catching the flu from you is negligible.

Now onto the vaccines. The grievance that I most frequently hear goes something like, "I got the vaccine and I got sick anyway. Flu vaccines are a scam." This argument indicates a misunderstanding of how flu vaccines work. No doctor or flu vaccine manufacturer claims that the flu vaccine is really all that great at preventing infection. What it can do, however, is decrease the severity of the illness that results.

Here’s what the Centers for Disease Control says about this year’s human flu vaccine:

Findings from early data suggest that this season’s vaccine so far is reducing the risk of having to go to the doctor for influenza by about 60% for vaccinated people. The data are published in "Early Estimates of Seasonal Influenza Vaccine Effectiveness — United States, January 2013," in the January 11, 2013, Morbidity and Mortality Weekly Report.

These estimates are within the range of what is expected during seasons when most circulating influenza viruses characterized by CDC are like the viruses included in the vaccine, which is what we are seeing this season. These findings also are similar to those published in a recent meta-analysis, which summarized the benefits of influenza vaccines using data from randomized controlled clinical trials. Influenza vaccination, even with moderate effectiveness of about 60%, has been shown to also reduce the following: flu-related illness, antibiotic use, time lost from work, hospitalizations, and deaths.

My family may have already experienced the flu this winter (I say "may" because we had typical symptoms but none of us were tested). We all received that vaccine early in the season. Between the four of us one did not become ill at all, two developed respiratory symptoms, and one had respiratory symptoms and a fever. No one was sick enough to warrant a trip to the doctor. If this was the flu, we got off pretty easy compared to what I hear some unvaccinated friends went through. This is what the flu vaccine can do for you.

The situation is similar for dogs that get the canine flu vaccine. The label for one of the available products states that studies have shown that the vaccine

reduced the incidence and severity of coughing
decreased the overall clinical signs of disease, including ocular and nasal discharge, coughing, sneezing, depression, and dyspnea (difficulty breathing)
reduced the days and amount of viral shedding
demonstrated protection against the formation and severity of lung lesions
is approved as an aid in the control of disease [note that it does not say "prevention of disease"] associated with canine influenza virus (CIV) infection

So, if you and your veterinarian have determined that your dog is at risk for canine flu (the vaccine is considered "non-core" and should only be given when circumstances warrant), understand that it may not prevent all signs of illness, but it should help your dog stay healthier than he would have otherwise.