The vaccine topic is a hot one.  And it should be.  Few other aspects of veterinary medicine invoke such strong dog owner opinions as the vaccine topic; and since immunology is such a complex science, it can be a challenging subject grasp.  Most dog owners today have read about “over vaccinating” dogs, have been exposed to opinions relating to purported vaccine-induced illnesses, and understand that any dog could potentially have an adverse reaction to any vaccine.  Nevertheless, millions of us continue to take advantage of the powerful science behind protecting dogs from truly devastating diseases.  The elusive and mysterious facts of immunology are rapidly being more understood, refined, and utilized for ever-improved methods of disease prevention.

Have you every wondered just what was in that syringe your veterinarian injected into your dog?  Did you have questions regarding safety, efficacy and frequency of administration?  Never be reluctant to ask questions because we become better stewards of our dogs the more we know about proper canine health care.  I recall a client who owned an unusual pair of fawn colored dogs… a Chihuahua and a Great Dane!  She asked me a very good question one day.  The two dogs were great pals, (by the way, the Chihuahua was the dominant partner of the two!) and came into the exam room together for their rabies vaccinations. 

I examined Thunder the Great Dane first, and then administered the vaccine.  After the physical exam on Chico the Chihuahua, I was just about to inject the rabies vaccine when the owner stopped me.  “Wait!” she said.  “You aren’t going to give him the same amount that you gave Thunder, are you?” 

She was concerned and puzzled that four-pound Chico was about to get a Great Dane’s dose of vaccine.  I spent a few minutes answering her very appropriate question about why the same volume (1 milliliter) of vaccine given to a 160-pound dog is also given to a dog 1/20 the size of Thunder.  I explained that with some types of substances, such as antibiotics, the appropriate amount to administer is body mass related.  With vaccines, though, decades of research show that for each bacterin or vaccine there is a minimum amount of antigen particles needed to be in contact with the dog’s tissues in order to stimulate appropriate immune responses and to build immunity.  So the critical issue is giving enough antigen to trigger a strong level of immunity.  If more than the minimum amount of vaccine or bacterin particles is administered there is not an “overdose” effect that one might find when other types of drugs or medications are given.  The dog either makes high levels of immunity or it doesn’t.

According to Fort Dodge Laboratory, a major manufacturer of animal vaccines and a leader in animal vaccine research, “When drugs such as antibiotics are administered to dogs, the dose depends on reaching a certain concentration of the drug’s active ingredient in the animal’s body. For this reason, a larger dog’s body mass requires a greater dose to achieve an optimal drug level. A vaccine dose does not vary based on body mass. Vaccines must stimulate the immune system above the threshold where the virus or bacteria is recognized as a foreign invader in the dog’s body. The immune system is then able to develop a protective response. This threshold appears to be similar in all dogs regardless of size.”

If she had not asked her question, Thunder and Chico’s owner would always wonder if I gave Chico “too much” vaccine.  It is common, too, for dog owners to wonder what is actually in that solution that is injected into the dog.  Fort Dodge states that although there is a wide variation in types and constituents in the various animal vaccines manufactured, the main ingredient in most vaccines is the vaccine antigen, a harmless derivative of the disease organism (bacteria or virus) in a form that triggers a protective response without causing the disease. Other ingredients such as preservatives, antibiotic and buffers are included. Occasionally, other immune stimulators are added to help improve the protective response.

Safety and effectiveness of vaccines is always a priority before any vaccine can be produced and sold to the veterinary market.  Because veterinarians have the awesome responsibility for animal health-care advice and management, the safeguards enacted and enforced regarding animal vaccines bolster my confidence as a veterinarian.  I know that strict regulations are in place regulating the manufacture and sale of vaccines for dogs. The United States Department of Agriculture’s (USDA) Center for Veterinary Biologics (CVB) regulates veterinary biologics (vaccines, bacterins, antisera, diagnostic kits and other products of biological origin) to ensure vaccines are pure, safe, potent and effective. The CVB develops appropriate standards and procedures for all aspects of a vaccine’s development, licensing and production. Additionally, CVB monitors a vaccine’s performance once it becomes commercially available; this is called post-marketing surveillance.

There are only a handful of manufacturers that meet federal regulations regarding interstate shipment of licensed vaccines. Major companies that have the resources for research and development of vaccines for dogs are Fort Dodge Animal Health, Merial, Pfizer Animal Health, Intervet and Schering-Plough Animal Health.  There are a few small vaccine manufacturers that do not meet federal regulations and cannot ship vaccines out of the state in which they were manufactured.  Major animal vaccine manufacturers are  continually involved in advanced research to improve existing vaccine technology.  For example, transdermal inoculation, where compressed gas, not a needle, is used to deliver a small volume of vaccine to skin tissues is already a reality and may be used in dogs and puppies someday soon.  This methodology may actually stimulate greater immunity and promises to lessen the incidence of local reactions.

Some pharmaceutical manufacturers are deeply involved with recombinant gene technology in an effort to improve vaccine specificity, purity and efficacy.  Vaccines utilizing recombinant gene technology have an advantage… their purity and lack of extraneous protein greatly lessens the chance that an adverse local or systemic reaction will occur.  Using precisely configured DNA sequences, scientists assemble a molecule that triggers the dog’s immune systems to create antibodies to specific diseases.  This spares the dog from receiving immune-triggering elements that are unnecessary and unwanted.  There is evidence that some of today’s very effective modified live vaccines may actually suppress a dog’s immune competence for a short time post-vaccination, and that is only one reason why the major vaccine manufacturers invest so much in manpower and financial resources toward development of better vaccines and delivery systems.