While we at McLean’s are certainly advocates for vaccinating our pets, vaccines are certainly a hot topic these days. One particular aspect of the vaccine debate that I find the general public may not understand is that of “herd (or community) immunity” and population medicine.
Whether we’re discussing a vaccine for our pets or ourselves, I find too often we focus on that pet merely as an individual, and neglect to consider the population within which that individual lives. “Herd immunity” (crudely titled from its agricultural roots) describes the immunity that exists in a large group of individuals (all the dogs in Toronto, for example) to a certain infectious disease agent because a large percentage of that group is vaccinated against that agent. For example, you need 85% of a human population to be vaccinated against diphtheria in order to prevent an outbreak. In other words, when 85% or more of the population is vaccinated, the disease cannot spread through the population because too many people are protected; it keeps hitting roadblocks of vaccinated individuals. When less than 85% of the population is vaccinated, the disease is able to spread through the population and cause an outbreak. This number (85%) varies with the virulence of the disease as well as the effectiveness of the vaccine. For most diseases, it varies between 75 and 95 percent.
So what does that mean to you or me? It means that if you never vaccinate your dog or cat and your pet never contracts these diseases we vaccinate against, it’s not that vaccines are unnecessary; it’s that enough of the other dogs and cats in the greater population got vaccinated and thus prevented the “bug” from ever getting to your pet. You could knock on your neighbour’s door and thank them.
Knowing and understanding this, it’s helpful and important to remember that how you care for your pet isn’t necessarily just about your one pet; it’s about the greater population health. Vaccinating your pet not only protects him or her, it also works to help protect all the dogs in the community, especially those who cannot receive vaccines for medical reasons. At the end of the day, like so many aspects of our lives, I think we should be asking ourselves: If everyone made the decisions I made and acted as I do, would the world be a better or worse place? Am I a part of the solution, or part of the problem?
Vaccinate your pets. We’re all in this together.
Written by: Dr. Sean Colyer