Would you want your beloved dog or cat to receive a vaccine if you knew pet vaccines contained a trace amount of mercury, or had a history of causing cancer or inflammation around the brain?
Would you be willing to pay a few extra dollars for a pet vaccine known to be safer, to cause fewer side effects, or to be more effective at protecting your pet?
Preventive medicine, for a lifetime of health and wellness, is a focus at Doylestown Veterinary Hospital (DVH). Vaccines are a part of preventive care, so the quality of the vaccines offered is important.
Do not assume all veterinary practices are equal when it comes to the type of vaccines being given. Drs. Laura and Randy Weis, co-owners of DVH, have put a lot of research into vaccines to choose those with the highest levels of safety and efficacy.
Safety and Efficacy of Pet Vaccines: A Few Examples
The goal with any vaccine, including pet vaccines, is to have a low incidence of unwanted side-effects and high efficacy. How the vaccine is designed and manufactured can determine how well the vaccine works, and incidence of side-effects.
Until about 20 years ago, all vaccines contained either a “killed” microorganism or a “modified live” microorganism. Today, some vaccines are made with newer technologies, which generally improve the safety.
Killed Vaccines
Vaccines using a killed (non-infectious) microorganism contain adjuvants, which are chemicals often added to cause inflammation at the injection site. The inflammation boosts the immune response to the inactive proteins in the vaccine. These vaccines also contain half a dozen to hundreds of proteins and other biochemical components that the body must raise immunity to, and that do not offer additional protection from infection.
Generally, this type of vaccine causes unwanted side effects and the duration of protection can be shorter. The added adjuvants can cause other problems, ranging from lumps of granulation tissue at the injection site to cancer.
In 1996, it was determined that adjuvants in killed rabies and feline leukemia vaccines were causing fibrosarcoma (a malignant tumor) in cats at the injection site. This type of Leptospirosis vaccine for dogs—used less often today but still available—has high rates of allergic reactions.
Modified Live Vaccines
Vaccines with a modified live microorganism contain bacteria or virus that has been altered—using chemicals, heat, or other means—to make the microorganism less dangerous to the host, yet adequate to elicit a protective immune response.
There are different risks and generally fewer side effects with modified live vaccines than with killed vaccines. Since the organism can cause low-level infection to elicit an immune response, the vaccine contains less foreign material. Since this vaccine interacts with the immune system more naturally, it can be more effective and provide longer immunity.
One risk is that the modified live organisms are inadequately weak, so the vaccine could cause a slight to severe form of the disease. This is less commonly a problem with modern techniques but has historically caused some dramatic morbidity and mortality. Another problem with modified live vaccines is the contamination of the vaccine with unknown viruses from the cells on which the vaccine is grown.
Sub-unit Vaccines
Sub-unit vaccines use a portion of the whole organism. These vaccines are less likely to cause unwanted reactions because of the reduced amount of irrelevant foreign material. This technique has made many vaccines better over the last 25 years.
The Leptospirosis vaccine used by DVH is a sub-unit vaccine with a better side-effect profile than other Leptospirosis vaccines on the market.
The Lyme vaccine used by DVH contains only one antigen and has delivered better than 99% efficacy over numerous years with only rare or mild unwanted reactions. Many Lyme vaccines on the market are only 65-75% efficacious with frequent unwanted reactions, and another is adjuvanted.
Vectored Vaccines
Vaccines can also be created using vectored technology. This method reduces the offending virus—such as with canine distemper—to one or a few specific genes. The codes for these genes are combined with a carrier virus that does not pose a danger to dogs and cats. The offending virus replicates slightly in the animal, transcribing its proteins, including the one or a few specific proteins from the virus. The dog produces antibodies against those particular distemper virus proteins, which confer protection to the dog against canine distemper.
Essentially, vectored vaccines have captured the best qualities of the two older vaccine manufacturing methods. The vaccine contains a small amount of foreign material, stimulates the body’s immune system with only the most relevant antigens, and tends to confer longer-lasting immunity since it’s a live organism presenting the antigen to the body. These vaccines tend to have fewer unwanted side-effects.
The Canine Distemper component of the DAPP (canine core vaccine) used by DVH is a vectored vaccine that eliminates encephalitis, one of the last serious side effects of the modified live Distemper vaccines. DVH gives the DAPP to dogs only every fifth year, as recommended in the AAHA guidelines, or runs titers to demonstrate adequate antibody levels.
The feline rabies vaccine and the feline leukemia vaccine used by DVH are vectored vaccines. The number of negative reactions to the vaccine is almost zero.
Other Factors
Vaccines often contain preservatives to prevent bacterial contamination that could be life-threatening to the animal. Thimerosal is a preservative containing mercury. Although pet vaccines containing thimerosal are being phased out, many are still used today. Thimerosal is the most problematic of the vaccine preservatives.
Doylestown Veterinary Hospital has not used any pet vaccines containing thimerosal since Drs. Randy and Laura Weis bought the practice in 2000.
The Cost of Quality Pet Vaccines
Quality pet vaccines cost more than vaccines made with older technologies. Generally, the cost difference is approximately $10-20 per vaccine. This cost is trivial compared to the monetary cost and emotional impact of treating a pet experiencing a mild or severe side effect, or worse yet, having the pet suffer temporarily or permanently from a disease easily prevented with a safe, effective vaccine.
When providing your pet with the best care for a healthy and happy life, the quality of the vaccines your pet receives over a lifetime should be an important consideration.
Core pet vaccines such as rabies should be given to all dogs and cats. Other vaccines, such as Bordetella and canine influenza, or feline leukemia, should only be given to adult animals if their lifestyle indicates sufficient risk.
Poor quality vaccines, vaccines administered more frequently than necessary, or vaccines that are irrelevant to your pet’s lifestyle can add unnecessary inflammation and negatively impact the pet’s health.
Preventive care is meant to keep your pet healthy while avoiding injury or stress to the animal, and eliminating costs associated with treating life-threatening diseases. One first line of defense is a quality pet vaccine that provides the best protection with the fewest, mildest side effects. A conversation about vaccines, including answering any of the client’s questions, is part of any wellness visit to Doylestown Veterinary Hospital.
