Puppy Vaccines:  Why Such Confusion?
Are they really Necessary?

Puppy Vaccines  by Janice Jones  |Last Updated 02-09-2023

Puppy vaccinations can prevent deadly diseases but they are not without controversy.  Why is there so much confusion over something as simple as puppy shots?

Experts know much about vaccines today, but there are also unknowns. 

There is little agreement even among veterinarians as to what is best for each dog.  What is worse, many people have heard horror stories about vaccine reactions in people.  With such controversy, wouldn’t it just be easier not to vaccinate at all?  Some think so, but read on.

Puppies are not naturally immune to diseases.   But, if their mother has been immunized or previously had the disease, she will pass on her antibodies via the placenta in utero.  Then the puppies will receive more protection once they have ingested their first milk. 

This first milk or colostrum is produced by the mother for the first 36 to 48 hours after birth and is rich in antibodies that the mother may have.  If the mother has none, she will not pass any protection onto her offspring.

Puppy VaccinesPuppy Vaccines

If Puppies are Protected, Why Vaccinate? 

The antibodies do not last forever.  Eventually, the puppy will not have the necessary level of antibodies needed to ward off the disease and will need a shot to protect him. 

If the pups continue to nurse, the maternal antibodies will protect the baby, but they will also block the effectiveness of any shots that might be given. 

The idea behind puppy shots is to time them in such a way so that once the level of antibodies is low enough the vaccine will work. 

Timing of Puppy Vaccines

There seems to be a wide window of time when puppies can be immunized successfully.  According to Dr. Fosters and Smith, only 25% of six week old puppies would have low enough levels of maternal antibodies circulating in their system to be immunized successfully. 

By nine weeks, the percentage of maternal antibodies rises to 40%, then 60% by 16 weeks and 95% by 18 weeks. 

Only one shot is needed to give the puppy protection from these deadly diseases for one year.

The trick is deciding when to give it.  If the pup receives the shot too soon, it won’t be effective; too late and the puppy is at risk of getting the disease.  This is why veterinarians recommend a serious of 3 shots, spaced 3 to 4 weeks apart. 

What are Puppy Vaccines?

Vaccines contain antigens that resemble the disease causing organism. 

There are three types of vaccines:

  • Modified Live Vaccines (MLV)
  • Inactivated or Killed Vaccine
  • Recombinant

Modified live vaccines contain a weak strain of the disease but since it was modified will not cause the actual virus.  These vaccines are considered to be quick and produce a long lasting immunity.

The inactivated or killed vaccine contains the killed whole disease agent.  It is the oldest method and is considered more stable, with the longest shelf life.  The immunity achieved is slower than the Modified Live Vaccine (MLV).  These vaccines require an adjutant to be effective.  Adjutant are chemicals that can result in increased risk of vaccine reaction. 

Recombinant technology is new providing respectable results.  These vaccines are some of the most advanced vaccines used in veterinary medicine. Recombinant vaccines use only portions of the selected genetic sequences. 

The vaccine does not expose the dog to the whole disease causing organism. The best benefit of Recombinant Technology is that the vaccine cannot become disabled by maternal antibodies like what happens with the other two types of vaccines.

What Puppy Vaccines Does Your Dog Need?

In 2011, the American Animal Hospital Association (AAHA) provided updated canine vaccination guidelines recommending timing of shots.  AAHA divided vaccines into three categories:  Core, Non-core, and Not recommended.

Core Puppy Vaccines:  Those Recommended Shots for All Dogs

Core vaccines are those suggested for all dogs because the disease is highly contagious, very severe or life threatening or have a chance of being passed onto people.  At present, there are four core vaccines, three of which are usually administered together in one shot.


Parvovirus is a contagious disease that can be fatal if not caught early.  It appeared out of nowhere in the early 1970s causing much suffering and death in dogs who were exposed which was a larger percentage of the canine population.

Vomiting and profuse, foul smelling mucus/bloody diarrhea are often the first symptoms seen in dogs, but fever (greater than 105 degrees F.) and severe lethargy is also common. 

Treatment consists of medications to control vomiting and diarrhea, IV fluids, and supportive care.

The AAHA recommends that puppies begin their shots between 6 and 8 weeks of age and then receive boosters every 3 to 4 weeks.  The last shot should be given between 14 and 16 weeks. 

Puppies should be vaccinated at one year of age and then about every three years.  Veterinarians often alter this schedule, so check with your vet for their recommendations.


Distemper is a disease that is potentially deadly.   It is caused by a virus similar to the one that causes measles in people.  An infected dog will shed the virus in all body secretions making it highly contagious.  Secondary infections and complications to this disease can occur.

Dogs suffering from distemper will have a fever, appear listless, stop eating and have a watery discharge from their eyes and nose.   If you think these symptoms sound like the common cold, you are right, but soon the nasal discharge becomes thick, sticky and yellow. 

Soon afterwards, vomiting and diarrhea occur.  The classic symptoms follow and include seizures, head shaking, chewing behaviors and slobbering.  Death usually follows.

Again, the AAHA recommends that puppy shots be given between 6 and 8 weeks of age, followed by boosters every 3 to 4 weeks until the last one is given between 14 and 16 weeks.

The vaccine is administered at one year and then every three years thereafter.  Distemper and Parvo vaccines are usually mixed in the same syringe and give with the Canine Hepatitis or Adenovirus vaccine below. 

Canine Hepatitis (Adenovirus-2)

Canine hepatitis (Adenovirus-2) affects the liver and can cause death.  It is highly contagious, and most cases in the US involve puppies younger than one year old. 

Symptoms can be mild or rapidly fatal.  In mild cases, the dog will lose his appetite and seem lethargic for a day or two.  In severe cases, the dog will develop diarrhea, high fever, vomiting, and abdominal pain.  The dog may also show signs of tearing or squinting, bleeding gums and jaundice.    

AAHA recommends that shots be initiated between 6 and 8 weeks of age, followed by boosters at 3 to 4 week intervals.  Puppies should receive their last shots between 14 and 16 weeks of age.  The vaccine is then administered at one year and then every three years thereafter.


Rabies is deadly and can be transmitted to humans through the saliva of an affected animal. Rabies has been identified in nearly all warm blooded animals.  In the United States, vaccination programs have reduced the risk to pets and their owners. 

Now, the major reservoir for this deadly disease is in wild animals-- skunks, raccoon, foxes, bats, and coyotes. 

Symptoms of rabies include disorientation, fever, increased aggression, and seizures.  End stages include paralysis, and frothing at the mouth.  Everyone agrees that this is an awful way to die.  If a dog is bitten by a rabid animal,  treatment consists of washing the wound with soap and water, and revaccinating the dog within 14 daysof exposure.

Rabies vaccines are mandated by law in the U.S.  The initial vaccine for Rabies is given between 12 and 16 weeks of age and then again at one year of age. The Rabies vaccine is the only shot that must be administered by a licensed veterinarian. 

All others can be given by anyone capable of doing so.  After the one-year booster, local law will decide how often the rabies vaccine must be given.  Most jurisdictions allow for rabies shots to be given every three years, but some require one or two year boosters.   

Non-Core Puppy Vaccines

Non-core vaccines include those given for a kennel cough (parainfluenza and Bordetella), Lyme disease, coronavirus, and Leptospirosis.  Non-core vaccines are those that are only given if your lifestyle or location warrants it.

Most non core vaccines either protect against treatable diseases or illnesses that don’t pose a universal threat. 


Kennel cough or “canine contagious cough complex and can be caused by as many as ten different microorganisms, but the two most common are Bordetella and parainfluenza.

Dogs get this disease in places where there are many dogs in confined areas such as a dog show, dog park, day care or boarding kennel.  It is spread through the respiratory tract.

Symptoms include a hacking cough but treatment is easy:  cough medicine and antibiotics. 

If your dog enters a boarding kennel or doggie daycare facility, he will likely need a Bordetella vaccine.  Vaccines are not shots but drops that are placed in the dog’s nose.


Leptospirosis is a disease affecting the kidneys and liver, and it is contracted through the contact with the urine of an affected animal such as a rat, raccoon, cow or pig.  The chance of a dog passing on Leptospirosis is rare but still considered possible.  That is why it is considered a non-core vaccine.

One problem with this vaccine is that it does not provide protection for more than about six or seven months.  The other problem is that there are four strains of Leptospirosis so the vaccine must be effective against all four.  Additionally, some side effects have been reported.

Read more about Leptospirosis in Small Dogs

Lyme Disease

Lyme Disease is a disease that both dogs and people can get.  It is caused by the bite of a tick. In dogs, symptoms can include lameness, kidney failure, and heart disease.  Sometimes there are no symptoms in dogs.

It is most widespread in the northeastern states of the United States, especially in New England, but also occurs in Wisconsin and Michigan.

The vaccine is administered in two doses, about 2 to 4 weeks apart and must not be given to puppies younger than 12 weeks of age. 

Annual vaccinations are recommended or given at the beginning of the tick season only to dogs known to be at risk. These would include dogs living in areas where Lyme Disease is prevalent or in dogs that regularly hunt, camp or are outdoors much of the summer months.

Not Recommended Puppy Vaccines

Those vaccines considered by the American Animal Hospital Association to be not recommended included

  • Corona virus
  • Giardia
  • Adenovirus-1
  • Rattlesnake venom vaccine


Corona is a rare disease that affects puppies younger than 8 weeks of age.  Symptoms include vomiting and foul smelling diarrhea accompanied by loss of appetite and lethargy.   

It is considered to be self-limiting, meaning that the puppies will get better on their own without any treatment. If treatment is available, it is supportive in nature,  and includes fluids if necessary and treatment of the vomiting and diarrhea.   

Dog owners rarely see this illness, because the puppies that may get the illness are still with the breeder.  Some veterinarians will still want to give your young puppy the Corona vaccine and then re-vaccinate in a couple of weeks.  Generally this is not necessary.

Corona virus is no a problem in adult dogs.  Veterinary Immunologists do not think the vaccine is effective.  The AAHA does not recommend it either.

This is one vaccine you can say no to without jeopardizing your puppy’s health.


A Canine Giardia vaccine is available but not recommended by the AAHA because the disease will respond quickly to treatment. 

Often worming medicines will treat this one celled organism along with other intestinal worms. 

If treatment is necessary it is supportive and includes maintaining hydration and treating any vomiting and diarrhea that may accompany this parasitic outbreak. 

Furthermore, there are risks of side effects.  The vaccine may adequately prevent Giardia infections.

Rattlesnake Venom Vaccine

This vaccine is specifically designed to produce antibodies against the venom of the western diamondback rattlesnake. It may also be work against other types of snakes including the Sidewinder, Copperhead, and Timber rattlesnake.  There is no protection if the dog is bitten by a  water moccasin or coral snake. 

Dogs require a booster after one month of the initial dose and then annual thereafter.  Because the positive effects of the vaccine diminish over time, twice yearly vaccines may be needed. 

If a dog should be bitten, they still require treatment, but may lessen the pain and amount of antivenin necessary for treatment. 

The AAHA does not recommend this vaccine due to the lack of information regarding its efficacy. 

Adult Booster Shots

Dogs will need booster shots to maintain full immunity from disease.  The frequency of boosters is very variable and depends on several factors:  the dog’s own immune system, the individual vaccine, and if the dog was exposed to the disease. 

Currently, the AAHA recommends re-vaccinating dogs every three years for most core vaccines. This does not mean, however, that immunity only last 3 years.  There is evidence that protection might last much longer, even the life time of the pet. 

Dr. Ron Schultz, professor and chair of the Department of Pathobiological Sciences at the University of Wisconsin School of Veterinary Medicine,  believes no booster is required for dogs assuming the initial dose is effective.

If vaccinating your adult dog seems like over-kill, you have a couple of options. 

Many holistic vets will recommend doing titers to determine the level of antibiotics remaining in the system.   This is a blood test and more expensive than giving the actual vaccine. 

The advantage of doing this before any vaccines are given are to protect the health of your dog. 

If you believe that too many vaccines are given today, this is a very safe alternative to submitting to an arbitrary vaccine schedule that may or may not adequately protect your dog without serious side effects.

Puppy Vaccines Adverse Reactions

According to Dr. W. Jean Dodds, immune-mediated blood disease, bone marrow failure, and organ dysfunction are rare but serious problems associated with the Modified Live Vaccines (MLV).  This is especially true for the distemper virus, adenovirus 1 or 2, and parvovirus. 

“The clinical signs associated with vaccine reactions typically include fever, stiffness, sore joints and abdominal tenderness, susceptibility to infections, neurological disorders and encephalitis, collapse with auto agglutinated red blood cells and icterus (autoimmune hemolytic anemia, AIHA, also called immune-mediated hemolytic anemia, IMHA), or generalized petechiae and ecchymotic  hemorrhages (immune-mediated thrombocytopenia , ITP).  Hepatic enzymes may be markedly elevated, and liver or kidney failure may occur by itself or accompany bone marrow suppression.”   

Sadly, veterinarians are not mandated to report any adverse reactions, so the actual incidence of problems is unknown.

Schedule for Puppy Vaccines

As a new puppy owner, it is often difficult to know what to do or what to expect when you see the vet.  Take a look at the following vaccine protocol schedules.  According to Pets Mart

DHLPPC (Distemper, Hepatitis, Leptospirosis, Parvo, Parainfluenza and Corona)

  • First vaccination: 6 to 8 weeks
  • Second vaccination: 9 to 11 weeks
  • Third vaccination: 12 to 14 weeks
  • Fourth vaccination: 16 to 17 weeks
  • Booster shots: 12 months


  • First vaccination: 14 weeks
  • Booster shots: 6 months


  • First vaccination: 16 weeks (varies by state)
  • Booster shots: 12-36 months


  • First vaccination: 14 weeks
  • Second vaccination: 17 weeks
  • Booster shots: 12 months


  • First vaccination: 14 weeks
  • Second vaccination: 17 weeks
  • Booster shots: 12 months

Puppy Vaccines Recommendations from AKC

Puppy’s Age Recommended Vaccinations

6 to 8 Weeks:  Distemper, measles, parainfluenza

Optional Bordetella

10 — 12 weeks:  DHPP (vaccines for distemper, adenovirus [hepatitis], parainfluenza, and parvovirus)

Optional:  Coronavirus, Leptospirosis, Bordetella, Lyme disease

12 — 24 weeks Rabies

14 — 16 weeks DHPP

Optional:  Coronavirus, Lyme disease, Leptospirosis

12 — 16 months Rabies, DHPP

Optional:  Coronavirus, Leptospirosis, Bordetella, Lyme disease

Every 1 — 2 years DHPP, Coronavirus, Leptospirosis, Bordetella, Lyme disease

Every 1 — 3 years Rabies (as required by law)

As you can see, there is much diversity when it comes to what vaccines to give at what times.  Your best bet is to contact your veterinarian and ask these important questions.

What vaccines are the most important for my puppy living in this area?

Why is it important that I vaccinate for non core disease?  Pros and Cons.

How big of a risk do I take if I choose to not vaccinate?

References and Further Reading for Puppy Vaccines

American Animal Hospital Association:  Canine Vaccination Guidelines

You might like these

About Janice (author and voice behind this site)

Having lived with dogs and cats most of her life, Janice served as a veterinary technician for ten years in Maryland and twelve years as a Shih Tzu dog breeder in Ohio.

Her education includes undergraduate degrees in Psychology with a minor in biology, Early Childhood Education, and Nursing, and a master's in Mental Health Counseling.

She is a lifelong learner, a dog lover, and passionate about the welfare of animals. Her favorite breed for over 50 years has been the Shih Tzu, but she has also lived with poodles, Maltese, Yorkshire Terriers, beagles, English bulldogs, carin terriers, and a Cocker Spaniel.

When not writing, reading, and researching dog-related topics, she likes to spend time with her eight Shih Tzu dogs, husband, and family, as well as knitting and crocheting. She is also the voice behind Miracle Shih Tzu and Smart-Knit-Crocheting

You might like these articles if

you found this one, Dog Training Tips for New Owners Helpful

Does This Article Deserve Your Thumbs Up?

We always appreciate your support and encouragement.  Your thumbs up means so much to us.  Please like this article.

If you find this page or any page on Small Dog Place Helpful, or useful in anyway, I'd love it if you would click the small heart found on the bottom right of each page.

You can also share or bookmark this page -- just click on the:

10 Mistakes People Make When Choosing a Dog Breed

Free Monthly Newsletter

Sign Up for Our Free Newsletter and get our Free Gift to You.

my  E-book, The Top 10 Mistakes People Make When Choosing a Dog (and how to avoid them)