Why Does My Puppy or Kitten Need So Many Vaccines?

Dr. Jacqueline Brister

What Vaccines Do

Vaccines are manufactured products that contain substances or organisms similar to the disease being vaccinated against. These organisms, such as bacteria or viruses, can be the actual disease-causing organism, but in an inactivated or nonliving form. They may also be living organisms that have been altered so that they are incapable of causing the disease upon vaccination.

Vaccines are given to stimulate your pet’s immune system to protect itself if exposed to the disease in the future. Once vaccinated, your pet’s body will produce antibodies to fight against the bacteria or virus, which will circulate until the effectiveness of the vaccine wanes. Some vaccines prevent your pet from being infected, while others decrease the severity of your pet’s symptoms and the ability of the bacteria or virus from spreading throughout their body.

Vaccination is needed not only to protect your pet but to help protect other pets that cannot be vaccinated. By vaccinating your pet, you are helping to create “herd immunity,” which greatly decreases the risk of disease outbreaks among pets in general and helps to keep diseases that can cross over to humans, such as rabies, from spreading unchecked.

Why Puppies and Kittens Need So Many Vaccines

Puppies and kittens are not born with the ability to protect themselves against specific diseases. Also concerning is that their immune systems are not as strong as an adult’s, so they are much more susceptible to catching a disease and becoming ill. The good news is that the mother will pass her disease immunity to her babies, which will help them fight off diseases if exposed. This immunity will eventually wane and the puppy’s or kitten’s own immune system will start to take over sometime when they are between 6 weeks and 12 weeks old.

The mother’s transferred disease immunity, also known as maternal antibodies or maternally-derived immunity, will counteract the vaccines. Her antibodies will prevent the puppy’s or kitten’s body from creating its own antibodies, essentially making those vaccines useless. Once the maternal antibodies are gone, the puppy or kitten will not have any specific protection against the vaccinated diseases. It is impossible to know the exact day or even the exact week that the maternal antibodies will leave the puppy’s or kitten’s immune system. To ensure puppies and kittens are protected from these diseases, they will need to be vaccinated every 2 to 4 weeks starting when they are between 6 and 8 weeks old and continuing until they are 14 to 16 weeks old.

Another reason why puppies and kittens need so many vaccines is that certain types of vaccines require more than one dose to provide protection. The first dose of vaccine exposes the immune system, preparing it for re-exposure and giving the immune system the opportunity to respond appropriately. The second dose causes the immune system to actually produce the antibodies needed to fight a future infection. Without the second dose, the prepping stage wanes over 2 to 4 weeks, and the body will need to re-prepare itself before producing antibodies. Maternal immunity again comes into play. If maternal immunity is present with the first, but not the second vaccine dose, the prep stage doesn’t happen, and the second dose will prepare the body but not produce the response needed for a future real infection. Thus, a third vaccine would be needed for the immune system to make the antibodies to fight the disease.

Common Diseases Vaccinated For In Puppies

  • Canine Distemper Virus: Highly contagious, often fatal, virus that is spread among dogs and some wildlife. Vaccination provides excellent protection.
  • Canine Parvovirus (Parvo): Highly contagious, often fatal, virus spread among dogs. Vaccination provides excellent protection.
  • Canine Adenovirus: Two adenovirus subtypes exist, both are highly infectious. Vaccination provides excellent protection against both subtypes.
  • Rabies Virus: Rabies virus is spread through saliva, often by a bite from an infected animal. Many animals are susceptible to rabies, including humans. Neurologic disease and ultimately death result from rabies virus infection. Vaccination offers excellent protection, but should not be given before 12 weeks of age.
  • Canine Parainfluenza Virus: Contagious virus that causes respiratory disease. Vaccination may not fully protect puppies, but it should greatly decrease symptoms if a puppy becomes infected.
  • Bordatella bronchiseptica (Kennel Cough): Contagious bacteria that causes respiratory disease among dogs and less commonly cats. Vaccination generally offers good protection, although some pets may still become infected. Vaccination greatly decreases severity and persistence of symptoms. Vaccination may not be effective for an entire year, so some veterinary facilities may recommended boostering puppy or kitten Bordatella vaccinations again at 6 months of age.
  • Canine Influenza Virus (Dog Flu): Canine influenza is an extremely contagious, sometimes fatal, respiratory disease virus. Two major strains of influenza virus can infect dogs, H3N2 and H3N8. Vaccinations are available for both major strains, but they do not fully protect from infection. Vaccination does decrease the severity and length of symptoms. Influenza vaccination is only recommended for areas with high risks for spread, such as areas with frequent outbreaks.
  • Borrelia burgdorferi (Lyme Disease): Lyme disease is caused by a bacteria associated with tick bites. The vaccine may not offer full protection if exposed to Lyme disease, but it will decrease the severity and length of symptoms. Vaccination is only recommended for areas with frequent outbreaks of Lyme disease.
  • Leptospira: Bacteria transmitted by dogs and local wildlife such as squirrels, deer, and raccoons. Humans are susceptible to Leptospira infection. Leptospira vaccines may not fully protect a pet from infection, but it should decrease the severity and length of symptoms depending on the strain of bacteria. Vaccination is only recommended for high risk areas with heavy wildlife populations (including squirrels).
Common Vaccines Used In Kittens
  • Feline Panleukopenia virus (Feline Parvo): Highly-contagious virus transmitted between cats. Most panleukopenia vaccinations offer excellent protection.
  • Feline Herpesvirus (Herpes): Highly contagious virus transmitted among cats. Vaccination may not fully protect a pet from infection but does decrease the severity, frequency, and length of symptoms.
  • Feline Calicivirus: Contagious virus spread between cats. Vaccination may not fully protect cats from becoming infected, but it will decrease the severity and length of symptoms.
  • Rabies Virus: Rabies virus is spread through saliva, often by a bite from an infected animal. Many animals are susceptible to rabies, including humans. Neurologic disease and ultimately death result from rabies virus infection. Vaccination offers excellent protection, but should not be given before 12 weeks of age.
  • Chlamydophila felis (Chlamydia): Contagious bacteria spread among cats. Vaccination may not offer full protection but does decrease the severity, frequency, and length of symptoms.
  • Bordatella bronchiseptica (Kennel Cough): Contagious bacteria that causes respiratory disease among dogs and less commonly cats. Vaccination generally offers good protection, although some pets may still become infected. Vaccination greatly decreases severity and persistence of symptoms. Vaccination may not be effective for a full year, so some veterinary facilities may recommended boostering puppy or kitten vaccinations every 6 months.
  • Feline Leukemia Virus (FeLV): Contagious, sometimes fatal, virus spread sporadically among cats. Vaccination may not fully protect against infection but can decrease the severity of disease.

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