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Written by leading veterinarians to provide you with the information you need to care for your pets.

The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Vaccination Programs for Puppies and Kittens

In my 30 years in veterinary practice I have had the opportunity to work in 20 different veterinary hospitals. Amazingly, in every practice, the clients, the staff, and, unfortunately some veterinarians did not understand kitten and puppy vaccination programs. They all thought that each vaccine was a booster to the previous and by the end of 16 weeks these babies were “super protected” and missing any vaccine was not life threatening. Nothing could be further from the truth. I would like to share the logic behind vaccination protocols in young animals.

Maternal Antibodies and Vaccinations

Unlike humans, mother animals cannot pass antibodies to their gestating babies prior to birth. The placenta of animals does not allow the transfer of immunity while in the uterus. Newborn animals receive their protective antibodies from the colostrums, or “first milk,” of mom. The intestinal tract of newborns will only allow the transport of entire antibodies in the colostrum from the intestines to the blood in the first 72 hours of birth. After that time period, colostral antibodies are treated like any other dietary protein: broken down and absorbed partially.

Provided that mom’s vaccine status is current, these newborns will be protected by the absorption of the antibodies in the colostrum. These antibodies will be their highest after consumption and decrease over time and disappear by about 16 weeks of age. During the time between birth and 16 weeks these maternal antibodies will protect the newborn against viruses, including those in vaccines.

Vaccines are designed to expose an animal or person to a modified version of viruses in order to stimulate immunity to these viruses without causing disease. Maternal antibodies destroy these vaccine viruses, so vaccines given when mom’s protective antibodies are high in the blood stream will offer no protection to young animals.

In any litter of kittens or puppies many antibody scenarios are possible:

  1. Mom has no vaccination history or has had only recent vaccines, so her colostrum has few antibodies.
  2. Mom’s vaccine status is great and all or some of the litter suckled well during the first 72 hours, receiving great antibody protection.
  3. Some newborns were poor at nursing and received few antibodies.
  4. Mom’s colostrum production or delivery was insufficient so the whole litter received inadequate antibody protection.
  5. Any combination of the 4.

Without blood testing for each virus, we veterinarians have no idea about the immune status of each newborn in each litter. This uncertainty has led to standard vaccination programs for young animals.

Vaccination Programs for Kittens and Puppies

Kittens and puppies are capable of responding to vaccines quite early in life. Those that did not receive adequate colostrum will respond to the initial vaccines and begin developing their own antibodies. Newborns that received adequate antibodies will not respond to vaccines because mom’s antibodies will interfere. Since we don’t know the status of each individual newborn or the exact time that colostral antibodies will be low enough to allow successful vaccination, we vaccinate every 3-4 weeks until 16 weeks of age. At some point during that period one or more vaccines will “take” and all newborns of any litter will be protected no matter when they started, with or without mom’s antibodies.

The number of vaccines an animal receives depends on when the vaccination program starts, not where it ends. The majority end at 16 weeks when we are certain colostral antibodies are ineffective. The earlier the programs begin the more vaccines the newborn will receive. Vaccination programs have nothing to do with “boostering.”

Many veterinarians recommend at least two sets of vaccines for kittens and puppies, starting with their vaccinations after 16 weeks. Whether this is necessary for all of the common viruses is subject to opinion and depends on the particular formulation of the viral vaccine. For instance, most veterinarians agree that it is probably a good idea to give two initial Feline Leukemia vaccines since the effectiveness of this vaccine to prevent disease appears to less than vaccines for other viruses.

Headway in research looks promising for vaccines that are not subject to colostral interference. This will allow a more defined vaccination program and reduce the number of initial vaccines.

Dr. Ken Tudor

Image: Thinkstock

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