The Vaccination Debate

Vaccines have long been known to be a beneficial part of the overall preventative health strategy for animals and humans. However, vaccines and traditional vaccination protocols have recently come under fire as people question if the risks of vaccines are worth the benefits that they provide. The remainder of this article will review what vaccines are, how they work, the benefits and risks of vaccination, the vaccine controversy, and recommendations for vaccination. Please note that this article is not intended to dictate a vaccination protocol for your pets but to help you, the pet owner, become more aware of the issues at hand.

What Are Vaccines?

Vaccines are made of whole organisms or portions of organisms (typically bacteria or viruses) that can cause disease. Vaccinations may also contain some sort of adjuvant or carrier and preservative. Vaccines can protect against single organisms, as with a rabies vaccination, or multiple organisms, as with a distemper vaccine. Vaccines are not available for every organism that causes disease. There are many diseases that do not have vaccinations available. 

How Vaccines Work

Stated simply, when a vaccine is given to an animal it stimulates the immune system to make antibodies. These antibodies are specific for whatever organism the vaccine is protecting against. The antibodies are then "stored" for future use. If the animal becomes exposed to an organism that it has been previously vaccinated for the antibodies will help prevent or minimize illness. 

The Benefits of Vaccination

The major benefit of vaccination is the prevention of disease or in some instances, the lessening of the severity of illness. For the single animal, the significance is obvious. Protecting our pets from undoing disease or illness is important. On a larger scale, disease prevention in large groups of animals, especially our food-producing species, such as cattle or hogs, is critical. If one animal in a herd becomes sick with a disease that the herd is not vaccinated for the outcome can be economically devastating. Massive illness and loss can occur. Another potential benefit of vaccination is to prevent human illness. There are several diseases that animals can transmit to people (i.e. zoonotic diseases). Some include Rabies, Salmonella, and Ringworm. If the animals that can spread these diseases to people are vaccinated then we (humans) get some protection against illness as well.

Potential Side Effects

Vaccines are drugs and like any drug, they can have side effects. The most common side effects are lethargy, pain at the site of injection, and swelling at the site of injection. These side effects are typically short-lived, often lasting less than 

24-48 hours, and mild. More serious side effects can include allergic reaction, autoimmune hemolytic anemia and, vaccine-induced fibrosarcoma, an aggressive tumor. These side effects can vary from mild to severe and are less likely to occur. For example, the rate of vaccine-induced fibrosarcoma is between 1 in 10,000 and 1 in 100,000 vaccinated cats. 

The Vaccine Opponents

Given the potential severity of some of the side effects of vaccination and the perception that some of the diseases we vaccinate for are rare or unseen, some people believe that vaccination is no longer necessary. This may or may not be true. Perhaps the reason that we do not see the diseases that we vaccinate for is that we have done a good job preventing them through aggressive vaccination protocols. Two examples of this theory can be demonstrated here. First, consider parvovirus. Parvo was a major killer of dogs when it first became widespread in the seventies. Since it was a new virus, dogs had no protection and became ill when exposed. When a vaccine was developed and used, the number of animals becoming ill declined because they were given advanced protection against the virus. Today, we still see parvo but not nearly as often as we used to. The animals that become infected with parvo are most commonly the animals that have not been vaccinated. Secondly, consider West Nile Virus, a modern-day virus that is new to the United States (first found in the US in 1999). In these, early years of the virus many birds, horses, and people are exposed and become ill because they do not have protection against the virus. A vaccine has been developed and is currently available for use in horses. As more and more horses are vaccinated, fewer will become ill with the virus. As vaccination increases, new cases of West Nile Virus in horses will become less common. Hopefully, a vaccine for humans will become available as well.

Alternative Recommendations

Another group recognizes the benefits of vaccinations but suggests that vaccines may protect against disease for extended periods of time. Currently, most vaccinations in veterinary medicine are re-administered annually. Rabies vaccines may be the exception, with every third-year revaccination, but this depends on state and county laws. The annual revaccination period is based on vaccine manufacturer recommendations. Most vaccine companies recommend annual revaccination of their products based on initial tests done for FDA approval. The problem with these initial tests is that they did not include studies to determine how long the vaccine lasted. Therefore, this information is largely unknown. A few smaller studies have, however, suggested that some vaccinations last longer than one year. Thus, this group recommends every third-year vaccination. 

There may be a few problems with this recommendation. First, there are no large, long-term studies that state exactly how long these vaccines last. Some animals may have protection for shorter or longer than three years. For animals with shorter immunity, they may be left unprotected with every third-year vaccination. Secondly, three-year vaccination protocols will not eliminate the side effects of vaccinations. Regardless of the length of vaccination, some animals will still have vaccine-related side effects.

Duration of Immunity

Duration of immunity is at the heart of the vaccine controversy. Duration of immunity simply means how long a given vaccination lasts. The biggest problem at this point in time is that there are no reliable, definitive means to determine how long a given vaccination provides protection. There have been attempts to quantify the duration of immunity through the use of titers. To determine a titer for a given vaccine, a blood sample is necessary. When a titer is taken, a laboratory will provide a number demonstrating immunity. This number is then compared to known protective levels and protection can be determined. For example, if we want to know if a dog has protection against a certain virus, a blood sample can be drawn and a titer can be run. Say the lab determines the titer to be 1:4 and protection has been determined to be at a level of 1:4. This would mean that the dog had adequate protection against the virus and additional vaccination is not necessary. Sounds easy, right? The problem with titers is complex. First of all, lack of a titer does not always mean that the animal is not protected. Second, titer technology is not available for all of the vaccines that are offered. Third, in many cases, there is not enough data available to determine what a protective titer is. So, if an animal has a 1:20 titer that may or may not mean that if an animal becomes infected with that pathogen it will not become sick. Thus, the duration of immunity is an important part of the controversy. If we knew how long vaccines lasted and had an accurate way to determine the level of protection, we would not be having this discussion.

What Should You Do?

At this point in time, given the information that is available on vaccination, there are several questions and concerns. First, what is the true rate of complications from vaccines? In my experience, mild vaccine reactions (lethargy, soreness, etc.)

are fairly common and rarely fatal. In the eight years since I graduated from veterinary school, I have seen two cases of vaccine-induced fibrosarcoma and one case of autoimmune hemolytic anemia. (i.e. these side effects have been very rare in my experience.) Second, if we decrease our frequency of vaccination will we increase the number of cases of the diseases that we are vaccinating for? Third, how can we easily and safely determine the duration of immunity and be assured that the data is correct and accurate? (i.e. if a titer tells us that the pet is protected, is it really protected?) 

Thus, given the current information, one should consider the risks and benefits of vaccines in relationship to the individual pet. How at risk is the pet for the diseases that we are vaccinating for? Typically, pets that are at higher risk for disease spend time outside, live in multiple households or have exposure to other animals, and/or have a history of fighting with other animals. There are certainly other risk factors and they vary by disease. How likely is the vaccine to cause side effects? This

is a difficult question as individuals vary greatly. Has the pet had side effects from vaccination in the past? Is the pet healthy or does he/she have a history of illness? Discuss these things with your veterinarian and come up with a reasonable plan for each individual pet. Hopefully, with time additional studies and testing methods will make the decision to vaccinate or not to vaccinate more clear-cut.

The information provided is for educational purposes only and is not intended to take the place of your regular veterinarian. Please do not hesitate to contact your regular veterinarian if you have questions regarding your pet.