How Important Are Vaccines?

In our industry, the discussion about vaccines has been raging. The debate is centered on which vaccines to use and how often to vaccinate pets to ensure that they are protected against many deadly diseases. Even though there is controversy surrounding vaccines, few will debate the benefit that vaccines have brought to the veterinary field. Vaccines have had the biggest impact on the lives and well-being of our patients. It has given us the ability to prevent infectious diseases that previously had been devastating to our patients.

How have vaccines changed?

The evolution of our vaccines has been an ongoing process. Early vaccines did not have the same safety and efficacy as our current products. Many times these vaccines had serious side effects with a short duration of immunities (DOI). Our previous recommendation to vaccinate every year reflects the limitations of these products. For many years, veterinarians worked on the “better safe than sorry” policy in order to prevent widespread outbreaks and devastating consequences.

The ultimate goal of any vaccine is to have 100% efficacy and 100% safety. Unfortunately, as of now, no vaccine exists that meets this requirement. There is not one current vaccine that is always protective, always safe, or always indicated. As our knowledge increases and newer generations of vaccines are brought to market, our recommendations on yearly vaccines are certain to be constantly changing.

Types of vaccines

To aid in the discussion of vaccines, some background and terminology will be beneficial. A vaccine is a preventive type procedure that involves showing the immune system a small part or a non-infectious part of a disease. The immune system will then mount a response to the disease so that when a pet becomes exposed to that disease, its immune system will be ready to fight.

Vaccines usually contain at least two parts. One part is the small part or non-infectious part of the disease for which we are vaccinating. The small part may be a modified version of the live virus. These vaccines are called Modified Live Vaccines (MLV). The small part may be a recombinant form or a viral or bacterial vectored vaccine. These are usually referred to as recombinant vaccines. The small part may also be the virus that has been killed. These vaccines are called Killed Vaccines.

The reason for the two different types of vaccines is that there are benefits and drawbacks to each. Modified Live Vaccines generally produce the longest and most solid immunity. Both pathways of the immune system, (humeral and cell-mediated) are activated. A single vaccine may provide significant immunologic memory, and may not need many boosters when given at the correct time. The drawback to an MLV is that it is possible for the vaccine to become live and cause the disease. This is a very rare occurrence, but can still happen.

Killed Vaccines cannot ever revert back to the live form and cause disease. However, they provide less durable immunity and usually require boosters. The rabies vaccine is a Killed Vaccine since this is a vaccine that we would never want to revert back to an infectious agent. Recombinant vaccines are also very safe. However, the duration of immunity is variable with these vaccines as well.

Why puppies & kittens need multiple rounds

Another interesting and important note about vaccines is that any vaccine given while a pet has circulating material antibodies from the mother’s milk is not effective. The maternal antibodies counteract the effect of the vaccine. This is one of the reasons we vaccinate younger animals multiple times to try and match when the maternal antibodies are falling, making the vaccine effective. For all the different diseases, the maternal antibodies fall at different times.

Which vaccines are necessary?

In our current discussion of vaccines, we have labeled some vaccines as core vaccines and others as non-core vaccines. Core vaccines are vaccines that should be given no matter what. Non-core vaccines are vaccines that are given to animals with a high degree of risk for developing the disease. For example, FELV is not considered a core vaccine for indoor cats since they have low exposure to this disease. It is, however, considered necessary for outdoor cats whose exposure is very high.

The newest guidelines for vaccinating dogs are as follows:

• Canine distemper virus (MLV): one dose should be given at 6-8 weeks, 9-11 weeks, and 12-14 weeks of age. A booster at 1 year, revaccination once every 3 years is considered protective.
• Canine Parvovirus (MLV): one dose should be given at 6-8 weeks, 9-11 weeks, and 12-14 weeks of age. A booster at 1 year, revaccination once every 3 years is considered protective.
• Canine Adenovirus-2 (MLV, Killed, or topical): one dose should be given at 6-8 weeks, 9-11 weeks, and 12-14 weeks of age. A booster at 1 year, revaccination once every 3 years is considered protective.
• Rabies 1-year: administered as early as three months of age. Annual revaccination.
• Rabies 3-year: administered as early as three months of age. Revaccination in 3 years
• Parainfluenza virus (MLV or MLV- topical): one dose should be given at 6-8 weeks, 9-11 weeks, and 12-14 weeks of age. A booster at 1 year, revaccination once every 3 years is considered protective.
• Leptospira interrogans combined with serovars canicola and icterhaemorrhagiae (killed bacterin): administer 1 dose at 12 weeks and a second at 12-14 weeks. Annual revaccination except in high-risk areas where vaccines are administered every 6 months.

In all, vaccines are a very complicated issue. Because our knowledge of vaccines and diseases is increasing every day, our current recommendations are likely to change over the next few years. The best advice when deciding about vaccines for your pet is to consult your veterinarian and look at the overall risk of disease for your pet.