My dog came home from the vet yesterday with a sore shoulder and a slightly bewildered expression. She had just received three vaccines: influenza, distemper, and leptospirosis. She already had her rabies shot, and I already knew why that one matters. Not only is it required by law in most states, but it also helps prevent the spread of one of the deadliest diseases we know.
But the others? Those are the vaccines people skip, debate, or forget to ask about. And that is a mistake.
Rabies gets the attention. It is dramatic, fatal, and familiar. The other vaccines do not inspire the same urgency, even though some of the diseases they prevent can be just as serious for dogs, spread much more easily in ordinary settings, and in at least one case can also affect humans.
So let’s talk about them.
Rabies Is Not the Whole Story
Most dog owners know about . Most , and the disease itself has a reputation that earns respect. Rabies is transmitted through bites, can spread from animals to humans, and is almost always fatal once symptoms begin.
But rabies is not the only dangerous infectious disease dogs face. Veterinarians also recommend vaccines for canine influenza, distemper, and leptospirosis because the risk is real. These are not fringe threats or theoretical problems. They are diseases with long histories, serious consequences, and well-established vaccines behind them.
Canine Influenza: A Fast-Moving Respiratory Disease
is, in simple terms, the flu for dogs. It is caused by influenza A viruses that have adapted to spread between dogs. In the United States, two strains have been especially important: H3N8, which originally came from horses, and H3N2, which has been linked to outbreaks after being introduced from abroad.
If that sounds familiar, it should. The basic public health story is one we have seen before: .
What makes canine influenza tricky is how easily it moves. Nearly every dog exposed to the virus becomes infected, and most develop symptoms such as coughing, nasal discharge, fever, and low appetite. Many recover within a couple of weeks, but not all do. Some dogs go on to develop pneumonia, often because of secondary bacterial infections, and those cases can become severe.
The bigger problem is that a dog does not have to look sick to spread it. Dogs can shed the virus before they seem obviously ill and sometimes for days after they appear better. That means a dog at daycare, a boarding kennel, a training class, or a dog park can pass the virus along before anyone realizes there is a problem.
That is one reason outbreaks can move so quickly. The made national news because thousands of dogs were infected across multiple states within weeks. Even when canine influenza is not spreading everywhere in the country at once, local outbreaks still happen.
The vaccine for canine influenza is considered non-core, which means not every dog needs it in the same way every puppy needs its core shots. But for dogs that board, go to daycare, attend grooming appointments regularly, visit dog parks, travel, compete, or live closely with other dogs, vaccination makes a lot of sense. Their lifestyle increases exposure, and the virus does not need much of an opening.
Distemper: An Old Disease That Still Deserves Respect
If canine influenza feels like a newer concern, distemper is the opposite. This is a disease with a long and ugly history.
has been documented for centuries. It is caused by , and that connection is not just a technical detail. Like measles, distemper is highly contagious and can affect multiple parts of the body at once.
It often starts with fever, runny eyes, nasal discharge, coughing, vomiting, or diarrhea. But in more serious cases, it does not stop there. Distemper can damage the nervous system, leading to seizures, muscle twitching, and progressive neurological decline. In some dogs, the pads of the feet and the nose become thickened and hardened, a classic sign of the disease.
Before vaccination became common, distemper killed large numbers of dogs. Mortality was especially high in puppies, whose immune systems are not yet fully developed. And distemper is not limited to pet dogs. It can also infect wildlife, including raccoons, foxes, skunks, ferrets, and wolves. That means unvaccinated dogs are not just at risk themselves. They can also become part of a wider chain of transmission between domestic animals and wildlife.
This is why . Puppies usually begin the series at 6 to 8 weeks of age and receive boosters until about 16 weeks. That schedule can feel repetitive to owners, but there is a reason for it. Young puppies are especially vulnerable, and immunity has to be built carefully and reliably.
The distemper vaccine has . Researchers spent decades figuring out the disease, identifying the virus correctly, and building a vaccine that was stable and effective enough for broad use. What we now think of as a routine core vaccine was not routine at all in the beginning. It was the result of slow, methodical work over many years.
Today, distemper protection is usually included in the combination vaccine that many owners know from the standard puppy series. It is so familiar now that it can seem almost invisible. But that familiarity is really a sign of success. We notice distemper less precisely because vaccination changed the landscape.
Leptospirosis: The One in the Backyard
may be the least familiar of these diseases, but it is arguably the one that should make people sit up a little straighter.
Leptospirosis is caused by bacteria spread through the urine of infected animals, especially rodents. Dogs can pick it up through contaminated water, mud, soil, or even through small breaks in the skin. A puddle, a wet patch of grass, a yard visited by a raccoon, a city alley with rats nearby, a park after heavy rain.
That is part of what makes leptospirosis easy to underestimate. People sometimes imagine it as a disease for farm dogs or hunting dogs in remote areas. That picture is outdated. Urban and suburban dogs get leptospirosis too, because rats and raccoons are not exactly rural exclusives.
And when dogs get sick, they can get sick fast. Leptospirosis can damage the kidneys and liver, sometimes within days. A dog may start with fever, lethargy, vomiting, or poor appetite and then worsen quickly. Severe cases can lead to kidney failure, jaundice, bleeding problems, and respiratory complications. Even dogs that survive may be left with lasting kidney damage.
There is another reason leptospirosis matters: humans can get it too.
This does not mean every vaccinated-versus-unvaccinated conversation needs to become apocalyptic. But it does mean this is not just a veterinary issue. Infected dogs can shed the bacteria in their urine, . Anyone cleaning up accidents, handling contaminated bedding, or living closely with a sick dog could be exposed.
That is why . The health of animals, people, and shared environments overlaps more than we often like to admit.
Older leptospirosis vaccines protected against fewer strains. Over time, as researchers learned more about which strains were circulating and causing disease, . Current vaccines are better matched to the real-world problem than older versions were. They require regular boosters, but that is not a sign of weakness so much as the reality of how this type of vaccine works and how this disease behaves.
In 2024, . That change reflected a shift veterinarians had already been seeing for years: risk is broader than people once assumed.
This Is Also a Public Health Story
There is a term for the idea that human health, animal health, and environmental health are connected: . It sounds like one of those phrases that can become a little too polished in professional settings, but the core idea is simple and important. What happens in animals affects people. What happens in the environment affects both.
That matters here. You see, a dog with leptospirosis is not just one sick animal. It can also be a link between wildlife, contaminated spaces, and human exposure. A dog with influenza can spread disease rapidly through a network of other dogs in kennels, parks, shelters, and homes. An unvaccinated dog is not an isolated decision floating in space. It is part of a larger web of contact.
At the same time, dogs are not just potential hosts of disease. They are companions, family members, and in many households, a major source of comfort and emotional stability. The evidence linking companion animals to better mental and physical health in people is substantial. Pets reduce loneliness, lower stress, and provide routine, connection, and affection. So when we protect their health, we are not doing something separate from human well-being. We are often protecting that too.
That is what makes these vaccines worth taking seriously. They are not random add-ons at the end of a vet visit. They are the result of years, and in some cases decades, of research, trial and error, surveillance, and improvement. They exist because these diseases caused enough harm for scientists and veterinarians to spend enormous amounts of time trying to prevent them.
And they work.
The Bigger Picture
Your dog’s vaccination appointment may feel ordinary. A quick visit, a few shots, a mildly offended look on the ride home. But it is also part of a much bigger system of prevention.
Every vaccinated dog is one less susceptible host. One less chance for an outbreak to spread. One less opening for a preventable disease to move through a kennel, a neighborhood, a wildlife population, or, in the case of leptospirosis, even a household.
That logic is not unique to veterinary medicine. It is the same logic behind childhood immunization schedules, seasonal flu campaigns, and outbreak control in human public health. The scale is different. The principle is not.
So yes, rabies matters. Of course it does.
But rabies is not the whole story.
If your dog is due for vaccines, or if you are unsure which ones make sense based on where you live and how your dog lives, ask your veterinarian. These recommendations are not arbitrary. They are built on evidence, experience, and a long history of trying to keep both animals and people safer.