Vaccination: Shield against canine diseases

Vaccination questions and answers


Immunizing dogs against disease seems to be a simple process; pet owners may even take vaccinations for granted. It is both the most routine procedure performed in veterinary clinics and also the one most prone to confusion and misconception. This article attempts to answer some common questions dog owners have about vaccinations.

How does a vaccination work?

In simplest terms, a vaccination stimulates the dog's immune system to protect itself against disease. When the antigen or infectious agent enters the dog's body, it is recognized as foreign and antibodies are produced to bind to it and destroy it. Even though the invader is gone, the cells that manufactured the antibodies "remember" it and will respond more quickly the next time the same agent is confronted.

Don't dogs get sick from a vaccination?

When vaccines were first being investigated, patients were actually given a less severe form of the disease or a related disease, with the idea that it was better to be a little bit sick now rather than a lot sicker later. Giving people cowpox to prevent smallpox was an early form of vaccination. Todays vaccines are attenuated (weakened), killed, or only pieces of the virus and don't actually transmit the disease.

What about vaccine reactions?

It is true that some animals have a systemic reaction, including a low-grade fever or muscle aches and pain. This reaction is more common in young and toy breed dogs and causes them to eat less and sleep more for 24-48 hours. Rarely, dogs will have a more severe reaction, characterized by hives, swelling of the face, or even vomiting. This reaction is easily prevented by giving antihistamine at the time of subsequent vaccinations. Leptospirosis, the component most likely to produce such strong reactions, can be left out of some vaccines. If your dog has had a vaccine reaction in the past, don't skip future vaccinations but do warn the veterinarian so he can take steps to prevent a recurrence.

Which is better, killed virus vaccines or modified-live types?

Each type of vaccine has strengths and weaknesses. Modified-live vaccines provide stronger, longer-lasting, and more rapid protection, including local immunity. They are less expensive and may require only one dose to be effective. They have a potential to become active and cause disease, especially in a patient with a weakened immune system; to create immunosuppression, or to cause abortions in pregnant dogs. Careful handling and storage are required to prevent breakdown of the active ingredients.

Killed vaccines cannot become virulent and are less likely to be immunosuppressive or cause abortions. They remain stable during storage. They are more likely to cause allergic reactions, require more initial injections and more frequent booster shots, and do not produce local immunity.

A good example of the differences between modified-live and killed vaccines is the use of Bordatella vaccinations for kennel cough. Killed vaccines require two injections but are only 60-80 percent effective against disease and don't provide local immunity at the level of the airway. Modified- live vaccines are given intranasally, require only one dose, and start providing local immunity within 48 hours.

Can you overload a puppy with too many things at once?

Probably not. Some researchers blame the rise of immunemediated disease on frequent vaccinations with large numbers of modified-live viruses. They feel this overstimulates the immune system, causing it to recognize everything as foreign and leading to tissue rejection. Currently, this theory is not accepted by most veterinary practitioners. Those who do adhere to this theory advise giving separate vaccination every few days instead of using combination vaccinations.

What this approach fails to consider is the interference caused by too-frequent administration of vaccines. Because the first shot will create a blocking effect and not allow the body to respond to a second or third shot a few days later, it is better to administer several antigens together than to divide the vaccines into many injections.

It sounds like vaccinations are dangerous. Is it worth the risk?

Absolutely! The risks associated with vaccines are slight compared with the risk of contracting a fatal disease like distemper, rabies, or parvovirus.

Shouldn't vaccines contain the most things possible?

No. Some people feel they receive a better value for their money if a vaccine contains six or seven or more antigens instead of the five-in-one combination most often used. Vaccination schedules based on your dog's age, breed, and lifestyle as well as your geographic location and your veterinarian's advice are more effective than trying to squeeze the most antigens into a one cc injection.

My dog was vaccinated against (parvo, kennel cough, etc) and got it anyway. Why?

Vaccine breaks occur for many reasons. Fever, steroids, disease, and maternal antibodies will block the patient's ability to make antibodies. Improper storage and handling of the vaccines or incorrect administration will also lead to vaccine failure. If given too close together, vaccines can be blocked by earlier shots; given too far apart, the memory response of the immune system is not properly stimulated.

Vaccines given to very young puppies (under six weeks of age) or to sick or immunocompromised patients may be ineffective. In the case of parvovirus, it has been demonstrated that Dobermans and Rottweilers are more susceptible to infection. Some veterinarians recommend extra vaccinations for these dogs or for dogs who are often in contact with other dogs.

How many shots does a dog or puppy need?

There is no one answer for this question, but a few basic rules apply. A minimum of two multivalent vaccinations (including distemper and parvo) given three to four weeks apart are required for every dog or puppy over three months old. An additional vaccination against rabies is also necessary. Vaccinations against coronavirus, Bordatella, or Lyme disease are based on owner's needs and veterinarian's advice.

For young puppies, vaccinations usually start at six-to-eight weeks of age and are given every three-to-four weeks until the puppy is 16 weeks of age. Recent information regarding parvovirus may extend this recommendation to 18 or even 20 weeks, especially for Dobes and Rottweilers.

[Is vaccination necessary every year?]

Kathleen R. Hutton, DVM

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