Vaccines 101

Aug 1, 2019   Tracey Aston   Vaccinations

Vaccines, sometimes referred to as “shots”, are a way to prepare a pet's immune system to fight off disease causing organisms.  Vaccinations play a critical role in protecting your pet from many dangerous and even fatal diseases. While state law requires all pets are vaccinated for rabies, there are a number of other vaccinations that can protect your pet from serious diseases that are easily preventable.

Simply put, vaccinations are given to protect your pet against disease. During vaccination, a modified bacteria, parasite or virus is administered to your pet by injection or intra-nasally. The vaccination triggers an immune response within your pet's body to protect against a specific disease. Vaccination is a procedure that has risks and benefits that must be weighed for every pet relative to his lifestyle and health. It's extremely important for pet parents to take the time to do your own research based on your pet's lifestyle, health and area you live in. For example, a healthy pet living in the city most likely wouldn't need a Lyme vaccine.

Vaccines contain antigens, which look like the disease-causing organism to the immune system but don't actually cause disease. When the vaccine is introduced to the body, the immune system is mildly stimulated. If a pet is ever exposed to the real disease, his immune system is now prepared to recognize and fight it off entirely or reduce the severity of the illness.

Core vaccines are considered vital to all pets based on risk of exposure, severity of disease or transmissibility to humans. Rabies is also required by law in most states PA included, unless there is a health concern. Pennsylvania is one of the few states that allows for a rabies exemption in the case of previous negative reactions, autoimmune disease and health concerns.

Vaccinations for both cats and dogs can be categorized into two groups: core and non-core. Core vaccines are recommended for cats and dogs with an unknown vaccination history. Non-core vaccines are optional vaccines that should be considered depending on your animal's risk.

Core vaccinations for puppies and dogs include:

·         Canine distemper virus

·         Parvovirus

·         Rabies

Non-core vaccines include:

·         Kennel Cough

·         Lyme disease

·         Leptospirosis

·         Giardia

·         Parainfluenza

·         Canine hepatitis (may come with combination vaccine of DHPP, which are not recommended for puppies or those with previous adverse reactions)


Core vaccines for kittens and cats include:

·         Feline rhinotracheitis

·         Feline calicivirus

·         Feline panleukopenia virus

·         Rabies

Non-core vaccines include vaccines for cats include:

·         Feline leukemia virus (FeLV)

·         Feline immunodeficiency virus (FIV)

·         Feline infectious peritonitis (FIP)

·         Chlamydophila felis

·         Giardia

According to Dr. Jean Dodds, the vaccine protocol should be as follows:



1st Annual Booster

Re-Administration Interval


Distemper (MLV) (e.g. Merck Nobivac DPV, or NeoVacD monovalent CDV only). Optional is recombinant rCDV = Merial Recombitek, but only comes in combo with CPV and Hepatitis/Adenovirus or more antigens

9-10 weeks; 14-15 weeks

At 1 year MLV Distemper/ Parvovirus only, or serum DPV antibody titers

None needed. Duration of immunity 7.5 / 15 years by studies. Probably lifetime.

Can have side effects if given too young (less than 8 weeks). Also can cause post-vaccinal encephalitis (PVE); see below.

Parvovirus (MLV) (e.g. Merck Nobivac DPV, or NeoPar monovalent CPV only)

9-10 weeks; 14-15;
18 weeks. In endemic parvovirus outbreaks, MLV CPV vaccine can be given at 6 weeks initially; then followed up with protocol above.

At 1 year MLV Distemper/ Parvovirus only, or serum DPV antibody titers

None needed. Duration of immunity 7.5 years by studies. Probably lifetime. Longer studies pending.

At 6 weeks of age, less than 30% of puppies are protected but 100% are exposed to the ubiquitous CPV.

Rabies (only killed)

20-24 weeks or as legally required. Use only thimerosal (mercury-free) rabies vaccine = Merial IMRAB TF-1, or Boehringer Ingelheim RabVac 1TF

1 year after puppy rabies (give 3-4 weeks apart from Dist/Parvo booster) Killed 3 year thimerosal (mercury -free) rabies vaccine = Merial IMRAB TF-3, or Boehringer Ingeleim RabVac 3-TF

3 yr. vaccine given as required by law in California (follow your state/provincial requirements)

Rabid animals may infect dogs or any other mammal including people.




Distemper @ 6 weeks or younger

Not recommended. At this age, maternal antibodies form the mother's milk (colostrum) will partially neutralize the vaccine, and giving MLV CDV vaccine earlier can cause vaccine-induced signs of distemper especially seizures and paralysis.

Parvovirus @ 6 weeks

In endemic parvovirus outbreaks, MLV CPV vaccine can be given at 6 weeks initially; then followed up with usual protocol above.

Hepatitis (Adenovirus 2) MLV often in a combo with CDV and CPV

Not preferred. Giving MLV CDV with Adenovirus-2 causes immune suppression for up to 10 days in puppies and increases chances of post-vaccinal encephalitis (PVE). Note: Merial Recombitek combo vaccine cannot cause PVE. IF adenovirus vaccination is desired, can give to older adolescents with oral or intranasal (not injectable)


Not recommended. Disease usually only affects young puppies that are malnourished and parasitized. Rare clinical disease. Mild self-limiting disease; produces orange-colored stool. Virus killed by 80 degrees F and dry housing.

Leptospirosis (4-Way killed vaccine)

Not recommended. Rare clinical cases; a reportable zoonotic disease, so check local veterinary and public health agencies for documented cases.
Vaccine side effects common. 4-way vaccine often contains the wrong serovars causing disease in local areas. There is poor cross-protection between serovars. Two doses initially needed given 3-4 weeks apart followed by yearly boosters.

Lyme Vaccine, Recombinant

Not recommended. Most cases are in Northeast and around the Great Lakes. Annual booster required after initial 2-dose series.

Bordetella (Oral or Intranasal) (killed bacterin). Injectable version (not recommended)

Generally not recommended. Oral preferred over intranasal, as it cannot spray vaccine around the face and those close by. Injectable not recommended as it does not release interferon to protect against the other upper respiratory viruses (kennel cough). Not 100% effective; may be required for boarding or grooming. Offer to sign written waiver to hold facility harmless instead.

Parainfluenza Vaccine (MLV)

Included as part of combo vaccines; but rarely clinically important or needed.

Influenza Bi-Valent H3N2/H3N8 Killed Vaccine

Being widely recommended as these viruses are highly contagious.
Not recommended routinely by Dr. Dodds as disease is mild and self-limiting unless fever is very high (>104 degrees F) and for those dogs harboring Streptococcus in their respiratory tracts.
Distinguished from common kennel cough which does not produce a fever unless secondary pneumonia follows in 7-10 days. Influenza produces a fever immediately.
2 doses required 3-4 weeks apart and boosted annually.


 While vaccines do provide health benefits to a pet, they aren't without side effects. Side effects from vaccinations range from mild itching and swelling to anaphylactic shock leading to death. Pets can develop vaccine sarcomas, which are cancers that develop at the site of the injection and even develop certain autoimmune diseases. There is an even larger chance of these reactions when giving combo vaccines, such as DHPP which is a combination of distemper, hepatitis, parainfluenza, and parvovirus.  If a pet has an aversive reaction to the vaccine, it now makes it much harder to pinpoint which vaccine caused the reaction and the pet may be put in danger in the future trying to determine which vaccine it was!  For pets that have had a bad reaction in the past, some vets are recommending taking Benadryl before vaccination, please know this is not enough to protect your pet from adverse and potentially deadly reactions and is an unacceptable practice. If your pet has had any reaction to a vaccine, they should never again be getting that vaccine!

It's imperative to weigh risk vs benefit in regards to yearly vaccinations. As clearly stated on all vaccine packaging, they are made to be given to healthy pets! Elderly pets, pets with health issues such as cancer or autoimmune disease or pets that have had a bad reaction to vaccines or the chemicals contained in them, should not continue to vaccinate their pets. Now, with new research showing that immunity may last longer than once thought, veterinary experts say it's safer to decrease the frequency of most shots that typically have been given every year.

If your pet had an aversive reaction, side effect or developed an autoimmune disease, please file a report with the FDA encourages veterinarians and animal owners to report adverse drug experiences and product defects associated with animal drugs or animal devices.

Pennsylvania is one of the states that will allow a rabies exemption for at-risk pets.  Pet parents should also consider titer testing for pet with health issues that may be exacerbated by yearly vaccinating. A titer test is a blood test that measures the level of immune system proteins called antibodies.

Vaccines do provide a health benefit to pets and have saved the life of pets, but pet parents need to be made aware of the risk as well. Take the time to discuss the benefits vs risks with your pet's health care professional and make an educated decision on what is best for your pet.  If you're vet isn't willing to share this information with you or be willing to discuss your concerns, check out our blog post Is Your Vet The Best For You and Your Pet.


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