Tan colored dog lying on table at vet with male and female volunteer staff petting him.

Why Does Your Dog Need Annual Flu Shots and Vaccinations?

Last updated on November 12th, 2023 at 04:13 pm

My vet from VCA Hospitals recently sent me an email informing me that my dogs should come in for their annual flu shots! Really? I already spent quite a bit of money getting them up-to-date on rabies, distemper and other key vaccinations prior to this email from my vet. But I was informed that Outbreaks of canine influenza virus, also known as the dog flu can occur anywhere, regardless of time of year even if it is not flu season.  This is also true of other highly contagious canine diseases.

So, I did some research. And, as it turns out, flu shots are now very important as well as other key vaccinations. There are two strains, H3N8 & H3N2, that are highly contagious and can cause your dog to be very ill for three weeks or more. In fact, flu vaccinations are just as important as other vaccinations such as distemper, rabies, leptospirosis, and, bordetella due to the high risk of severe illness and even death.

Keep reading to learn more about veterinarian recommended flu and other critical canine vaccinations.

Canine Flu Viruses

Recent History of Serious Flu Outbreaks

Sick pug wrapped in a blanket.
Pug with the flu.

Currently, two strains of Type A canine influenza exist in the United States. In 2004 a strain labeled H3N8 was identified in Florida in racing greyhounds. It was presumed to have jumped from race horses to dogs. Over the past several years, the virus has spread quickly and now seems to be present in every state.

In 2015 a new outbreak of a serious virus, the spread of the disease caused high fevers, hacking coughs, dripping noses, runny eyes, lethargy, and loss of appetite, infected 1,500 dogs in Chicago and caused at least 8 deaths. It soon spread to 25 other states leaving veterinary clinics feeling overwhelmed and perplexed by this new canine virus labeled H3N2. It had previously been an avian virus originating in Asia, but now it was infecting dogs at an alarming rate.

Even though the death rate was not exceedingly high, the seriousness of the illness was a huge concern. Veterinarian practices in the Chicago area became overwhelmed with tough cases that required hospitalization for a high number of dogs. Dogs remained sick for up to three weeks or more and the virus was highly contagious. Dogs who went to dog parks, groomers, kennels, or a daycare facility were considered at high risk for picking up the H3N2 virus. Older dogs were more also vulnerable to picking up a flu virus.

The Argument For and Against Vaccinations

Arguments Against Canine Vaccinations

As with any medical intervention, some people have concerns about whether or not certain procedures are necessary. This has been true of vaccinations as well for the past many years. Here are some of the reasons people are hesitant:

  • Some pet owners do not want to pay for the cost of preventative healthcare
  • Vaccines do not always work 100%
  • Vaccines are thought to be bad for both humans and their pets due to toxic agents such as preservatives or “dead bugs”
  • Pet owners do not always believe that canine vaccinations are necessary
  • Others believe that only the legally required vaccinations are important
  • Vaccinations can have some side effects

Anti-vaxxers have been around for a long time. I have to admit that I sometimes have concerns about my own vaccinations at times, as they do have side effects. However, when I think about the seriousness of illness that vaccinations can prevent, I will gladly hold out my arm for a shot. Let’s take a look at the many benefits.

Deadly canine viral and bacterial illnesses have been around for hundreds of years. Therefore, we are fortunate that in the last century scientists have developed vaccines for both humans and animals that have saved countless lives. One infected dog can cause an entire population of healthy dogs to develop severe cases of illness.

Senior dogs and dogs in a boarding facility may be at greater risk when exposed to a sick dog. Contaminated water bowls at dog parks and other shared areas along with flu season are other factors that need to be considered regarding the general dog population. Here are some of the benefits of canine vaccines:

  • Canine vaccines have been around for over 60 years and have a long track record of being safe
  • Dog vaccinations are cost-effective averaging $30-$40 per shot as opposed to $1000’s of dollars to treat life-threatening illnesses
  • Vaccinations can prevent death, serious illness, or permanent disability
  • Injections are almost painless due to the thickness of a dog’s skin
  • Your dog will live longer and have fewer complications
  • Side effects are usually very minor and brief

For our furry friends, severe strains of canine influenza are relatively new. Some people may scoff at the idea that it is important. However, any dog who has contact with other dogs can be at high risk.

What Vaccinations Are Necessary for Good Canine Health?

There are three types of vaccinations that dogs need:

  1. Core vaccinations are required by law, and/or facilities that care for dogs.
  2. Key preventive vaccinations are not necessarily required by law but are highly recommended by vets and sometimes required by kennels and daycare facilities to protect against serious, highly contagious diseases.
  3. Regional vaccinations recommended on a regional basis can protect against viruses, bacterial infections, or poisons carried by vectors such as ticks and snakes.

Almost all states in the United States now require rabies shots. Most states and counties require dog registration and tags along with proof that your dog has had his rabies shots. Dog owners will usually need to show proof of rabies shots if his dog bites someone–if not, the owner could be subject to fines.

Getting all of the recommended core vaccinations and the annual flu shot is a good idea to reduce the risk of infection. If you are planning on adopting a dog from a shelter, make sure you check his medical history to ensure he has had at least the core vaccinations. Then be diligent about keeping up with his boosters. See my post “How to Tell if a Rescue Dog is Healthy Before You Adopt for more information.

Core and Other Key Vaccinations

DescriptionWhen Needed
Core Vaccinations
Rabies Rabies is a fatal virus common in all mammals. Required by law in most states.
Distemper, Hepatitis, Parainfluenza, Parvovirus (DHPP)All in one shot for serious, life-threatening viruses.Recommended by most vets as critical for good health. May be required by law as well as kennels/daycare facilities
and groomers.
Leptospirosis A bacterial disease that is prevalent in moist climates. Can spread from animal to human. If you take your dog to the beach, lake, river, or live in a very
moist/wet area with slow-moving water, your dog will
need this shot.
BordetellaA virus often called “Kennel Cough” is highly contagious and causes upper respiratory infection. If you take your dog to dog parks, kennels/daycare facilities, groomers,
and vets strongly recommend this vaccination. Some
facilities/groomers require it.
Canine InfluenzaH3N8 & H3N2Vets have been recommending these since serious outbreaks in
2004 and 2015 due to their highly contagious nature. If your
dog interacts with other dogs a lot, these are important
Lyme DiseaseA serious bacterial disease spread by ticks.More prevalent on east and west coasts and Great Lakes regions.
Check with your vet.
Corona VirusThis is a non-Covid-19 virus that infects the intestinal attract. This disease is more prevalent in the south. In most parts of the
The United States, most vets do not think the benefit is significant
enough to warrant this vaccine.

To protect against diamondback rattlesnake bites. This is usually only recommended in the Western United States or areas where a dog may be exposed to rattlesnakes. Check with your
vet to see if your dog needs this.
Table of Dog Vaccinations

When Should Your Dog be Vaccinated?

Vaccination schedules will vary depending on the age of your dog. Puppies usually can have their core vaccinations when they are around 8-16 weeks old. Vets will usually vaccinate senior or elderly dogs less frequently, so their immune systems will not be overwhelmed. See my post How to Help Your Senior Dog Stay Healthy and Live Longer for more information about older dogs. Also, see the caninejournal.com post for more detail about the vaccines and timing. Below is a summary of when to administer shots:

Vaccination Schedule for Key Dog Vaccinations

PuppiesAdult Dogs
Core Vaccinations
RabiesSingle dose around 16 weeks old1 dose year after puppy vaccines; then every 3 years
Distemper, Hepatitis, Parainfluenza, Parvovirus (DHPP)3 doses between 3 & 16 weeks old1 dose a year after puppy vaccines; then every 3 years
Other Vaccinations
Leptospirosis2 doses 2-4 weeks apart between 6 & 12 weeks oldAnnually or bi-annually
Bordetella2 doses 2-4 weeks apart between 6 & 12 weeks oldAnnually or bi-annually
Canine Influenza2 doses 2-4 weeks apart between 6 & 12 weeks oldAnnually or bi-annually
Regional Vaccinations
Lyme Disease2 doses 2-4 weeks apart after 12 weeks oldAnnually or bi-annually
Corona Virus (non covid-19)at or after one year old Not generally recommended by vets due to lack of efficacy.
Rattlesnake Envenomationafter 12 weeks oldEvery 6-12 months
Vaccination Schedule for Dogs

Diseases and Symptoms of Canine Influenza

Just as humans have battled serious diseases such as smallpox, polio, measles, and now Covid-19, our canine friends are prone to some serious illnesses as well. Therefore, just like us, dogs need certain vaccinations to stay healthy and prevent serious illness or even death. Vets have vaccinated dogs for the last 30-40 years for a handful of diseases such as rabies, parvovirus, and distemper. As new diseases emerged over the years, more vaccines were developed. Be sure to see my post, Common Health Problems of Strays and Shelter Dogs for more information. Here are some of the more common illnesses that your vet worries about:

Core Disease Concerns


Rabies is a horrible virus that is a concern for your dog and any animal or human he might bite. It is classified as a zoonotic disease meaning that it can pass from animal to human, and any mammal can contract it. Since biting is the primary way this gets passed, anyone who is bitten should immediately get medical help. This is true even if your dog is up-to-date on his rabies boosters. Humans often need a series of shots to counter potential rabies illness if bitten by a dog without a vaccination or who has an unknown medical history.

The Caninejournal.com posted an article by Kimberly Alt on March 16, 2021 that described the symptoms of rabies: “Rabies’ symptoms include fever, paralysis, seizures, a dropped jaw, inability to swallow, hydrophobia (fear of water), pica (eating non-food items, like dirt), a change in bark tone, unusual aggression, lack of coordination, excessive salivation, and frothy saliva.”

Alt goes on to describe the “furious and paralytic” stages in which behavior becomes confused and aggressive, thereby coining the phrase “mad dog” syndrome. This furious and aggressive stage is quickly followed by paralysis and death, which is why rabies disease is so feared. As a result, vaccinations are mandated by almost all states and counties.


Distemper is a highly contagious virus that passes through the air and can impact most bodily systems. This vicious disease usually attacks the tonsils and lymph nodes and spreads to the GI tract, respiratory, and nervous systems. Puppies living in settings with other dogs are very prone to picking up this nasty virus, which will quickly overwhelm their developing immune systems So it is wise to get your puppy vaccinated as soon as he is old enough. Additionally, other wildlife can carry this virus, so dogs who are exposed to wildlife during hikes through the woods have greater risk.

The symptoms are extensive starting with high fever, runny nose, coughing, red eyes, nasal and eye discharge, lethargy, poor appetite, vomiting, and diarrhea. As the disease progresses, it can lead to seizures and eventually paralysis. The American Kennel Club describes the two stages in an article written November 15, 2016 by Anna Burke, entitled Distemper in Dogs. Her description and prognosis is grim, especially for puppies under four months old.

Some dogs do recover, however, and will no longer pass the virus on once their symptoms have resolved. However, this is a totally preventable disease by having your puppy or adult dog vaccinated on a regular basis.


This disease, also known as adenovirus type 1, causes swelling and damage of the liver and eventually hemorrhaging and death. Symptoms include abdominal distension and pain, poor appetitive, fever, lethargy, and tonsillitis. It is passed from dog to dog through feces and urine of other infected dogs.

Another related disease is the adenovirus type 2 which is another cause of a syndrome sometimes referred to as “kennel cough”. Symptoms include a hacking cough with a foamy discharge, inflamed airways, pink eye, and nasal discharge.


Parvovirus is another serious concern for puppies as well as adult dogs. Since puppies have less developed immune systems, they are less likely to recover. Additionally, puppies often live with other puppies and dogs until adopted out, and parvo is passed through feces and shared food dishes.

Symptoms develop quickly within 3-10 days of exposure and include dehydration, lethargy, diarrhea, vomiting, endotoxemia, and shock. This disease can weaken the immune system and lead to secondary infections. The death rate for this severe illness is a shocking 91%. However, it is totally preventable with vaccinations starting with puppies who are around 8-12 weeks old.


This virus is not the same as seasonal canine flu and is related to the parvo virus. It is a very serious upper respiratory cough that is sometimes also called “kennel cough”. Symptoms usually involve severe lethargy and coughing along with low grade fever and poor appetite. Some vets do not consider the vaccinations to be core, but often include it as part of a combination core shot.

Other Serious Illnesses


Leptospirosis is another zoonotic disease caused by a bacteria. It is usually picked up in standing water that has been contaminated by the infected urine of another animal. The vaccination for this disease is highly recommended, but not a core one since only 10% of cases lead to acute illness or death. However, it is still a very serious illness which impacts a dog’s kidneys.

A dog’s symptoms can include fever, pain, vomiting, depression, loss of appetite, and conjunctivitis. As the disease develops a dog may have increased thirst, more frequent urination along with a change in urine color. Later symptoms may lead to dehydration, tremors, vomiting, bloody stools, and trouble breathing. Therefore, even though this is not considered a core vaccination, it is still very important for any dog who travels to parks, beaches, lakes, or is around other animals in community settings that may include water or shared water sources.


Bordetella is highly contagious bacteria that is most commonly described as “kennel cough”. It is passed through the air and it’s most notable symptom is a high pitched, hacking cough. Other symptoms include fever, nasal discharge, sneezing, loss of appetite, lethargy, and depression.

Because it is so highly contagious and passed through common spaces, cages, and feeding bowls, many kennels will require that your dog is vaccinated for Bordetella two weeks prior to being boarded.

Canine Influenza

The two known serious flu strains, which I referred to at the beginning of this article are the H3N8 and H3N2 types of seasonal dog flu. They are less acute then they are contagious, but they do cause some nasty symptoms which your dog will have for several days. Just as with us, annual shots can prevent a serious bug from taking hold that might also lead to other complications.

Regional Diseases

Depending on where you live, your vet may have different recommendations for protecting your canine pals. Many years ago, I lived in Arizona and hiked a lot in the desert and wilderness parks. If I lived there now, I would definitely get a rattlesnake bite vaccine given to my dogs!

I used to have Lyme disease, so I know how serious this illness can be. However, I am skeptical of Lyme vaccinations as they did not work well for humans several years ago. Furthermore, the ticks that harbor and spread Lyme disease also carry other viruses and bacteria that make Lyme disease very complex.

Therefore, there is not just one vaccine or medicine that can deal with the whole complexity of what we call Lyme disease for humans or dogs. However, I still recommend that you check with your vet. In some parts of the country, especially in the Great Lakes area, there may be a specific and more prevalent type of bacteria carried by ticks in that area. In this case, a canine vaccination may be useful.

The coronavirus (non Covid-19) disease is not usually considered worth getting according to The American Animal Hospital Association. Their recommendation stems from the fact that it usually impacts puppies less than 6 weeks old, who are too young for a vaccination. Also, the disease it causes is generally self-limiting and mild.

But always check with your vet. There may be other recommendations pending where you live and your dog’s life style.

Most researchers and vets believe that the benefit of vaccinations outweighs the risk. They also point out that the rare, but negative reactions to canine vaccinations also occur in humans as well. And, any medical intervention can carry some adverse results.

In Summary

Charlotte and Georgia having fun at doggy day care!

I want my dogs to have a happy, healthy life. We go to the beach, the park, hiking, and dog parks. They also enjoy the occasional romp with other dogs at the big open field at their favorite doggie day care. Therefore, I make sure they have all of the core, key, and seasonal flu vaccinations that my vet recommends. For more information about adopting and caring for dogs be sure to see my post, Everything You Need to Know About Adopting Rescue Dogs.

Yes, it costs a little bit more. But it eases my mind, gives my dogs a lot of freedom to play with other dogs, and keeps them in good health and high spirits!

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