Strictly speaking, a vaccine is a preparation of killed microorganisms, living attenuated organisms, or living fully virulent organisms that is administered to produce or artificially increase immunity to a particular disease. The goal is to present the virus in as natural a way as possible so as to accurately mimic the stimulation obtained by natural infection, yet avoid the illness normally experienced in conjunction with the pathogen. Once presented with the pathogen at low concentrations, the body’s immune system will in the future recognize the substance as harmful and will attack any viral particles that may enter the body before they have a chance to replicate.

The Vaccination Process

Each vaccine is administered by injection, introducing either modified or killed versions of pathogens to the body. The immune system recognizes the germs as harmful and proceeds to manufacture special proteins called antibodies. These antibodies will “remember” that specific germs and viruses are bad, and will be prepared and able to fight the real disease should your pet be exposed to it again. This state of having memory cells capable of fighting of viral diseases is known as immunity.

Killed versus Live Vaccines

When administering a killed vaccine, no active viral particles are being injected into the patient. Rather, vast amounts of dead virus are injected and gradually filter into and trigger the immune system. Live vaccines involve the injection of live but modified viral particles. The virus has been altered in such a way as to prevent full-blown infection. The benefit of using a live vaccine is that the triggered immune response is much more realistic and, in some cases, more effective. Despite the small risk of infection associated with live vaccine, it has been clearly documented that killed vaccine produces far inferior results, and live vaccine is recommended in nearly all situations.

What is a “High Titer” Vaccine?

High titer vaccines are relatively new inventions. They contain especially high concentrations of modified live virus. There is enough virus in these vaccines to stimulate the immune system with a great deal of effectiveness, yet not so much that they will induce harm. Studies have shown these high titer vaccines to be capable of producing satisfactory immunity by 12 weeks of age – 4 weeks earlier than the more traditional shots. By continuing the vaccination through 16 weeks of age with high titer vaccines, a much better level of immunity may be achieved. Most state of the art combination vaccines on the market today are of the high titer variety.

Potential Side Effects Associated with Vaccinations

Side effects associated with receiving a vaccination are minor, and may include muscle soreness, lethargy, and low grade fever. Symptoms may persist for a day or two, and are merely indications that the immune system has in fact been stimulated and is working overtime. Allergic reactions are uncommon but possible. If facial swelling or hives occur, care should be taken when administering any future vaccines, as reactions generally worsen with each exposure.

There has been recent concern regarding the possibility that vaccinations could trigger the onset of cancer. Preliminary studies have suggested that in rare cases vaccinations may induce fibrosarcomas in cats. The rate at which this occurs however is estimated to be extremely low – only between 1:1000 and 1:10000, and no link between vaccination and cancer in dogs has been found.

Why must my dog be vaccinated so many times?

At birth, mammals receive all their nutrition from their mother’s milk. This milk contains not only calories, vitamins, and minerals, but also important immunities to various diseases. Thus, for the first few weeks of life, puppies are safe from viruses thanks to their mother’s immunity. By the about the 5th week of life however this maternal immunity begins to wear off and the puppies become vulnerable to germs. This is why vaccinations are begun so early, starting at approximately 6 weeks of age.

It is necessary to repeat the vaccinations every 3-4 weeks until the puppy reaches 16 weeks of age because at first the maternal antibodies that were once so helpful may be interfering with the effectiveness of the vaccine. It is estimated that these maternal antibodies prevent vaccines from working in 75% of 6 week olds and 25% of 9 week olds. There is of course no way to know which group your puppy belongs to, so it is important to adhere to the vaccination schedule recommended by your veterinarian.