Sylvester was right to chase Tweety!
By: Dr. Daniel Eubanks
To vaccinate or not to vaccinate.
This decision frequently confronts pet owners, veterinarians and human patients alike.
Let’s review the facts of older vaccine technology and take a look at some refreshing and reassuring new concepts.
A vaccine is a preparation of an altered form of a pathogen virus, bacteria, etc. administered to a patient with the intention of inducing that patient to produce his or her own protective antibodies against that particular organism. The pathogen is altered in one of several ways so it induces the immune response but does not produce the disease in the patient.
For decades, the trend was "more is better." Vaccine combinations often contained six or more disease pathogens.
If there was a disease out there, the pharmaceutical industry would respond by creating a vaccine for it. They even created a vaccine for which they had to invent the disease!
Vaccines were given indiscriminately, and boosters were given every year simply because the manufacturer found it unprofitable to document longer duration of immunity.
Vaccines, like all medicines, have inherent potential side effects, especially the older ones. They are a stress on the patient’s immune system, demanding it gear up and perform some work.
In some instances, they can cause transient immunosuppression or autoimmunity confused antibodies that can’t differentiate invader from "self." Sometimes additives to the vaccine called adjuvant are responsible for adverse reactions.
Well, within the last decade, two trends converged on the "more is better" philosophy consumer awareness and improved technology. Consumers patients, owners, veterinarians are more skeptical of indiscriminate vaccination and have become more selective. This "less is better" trend includes carefully selecting only appropriate vaccines for the patient and minimizing boosters.
Currently, our veterinary associations advocate a core of essential vaccines for each species, and all others are optional, catered to the individual’s exposure potential.
The pharmaceutical firms who manufacture the vaccines also are cooperating. They are advancing developmental technology to minimize or, in some cases, eliminate potential side effects and performing the necessary studies to extend and document duration of immunity, thus reducing booster frequency.
A brief history of vaccine evolution makes one appreciate this new technology.
The oldest, rudest and crudest vaccine is the killed type. Here the whole, entire pathogenic organism is killed so it cannot cause the disease. It then is thrown into a blender with a little seasoning, put into a vial, and there you have it the most primitive vaccine.
Injected into the patient, this presents a massive, random antigenic challenge. Most of these antigens are not even required for the induction of immunity. Typically, only one or a few specific outer surface protein antigens are responsible for immune stimulation. All excessive and unnecessary antigens simply increase the likelihood of adverse reactions.
Killed vaccine is also by definition only a weak stimulant to the immune system. An additive called adjuvant must be included to intensify the immune response. Adjuvant is notorious for causing side effects.
Modified live virus vaccines evolved next as an alternative to killed. Here the pathogen is modified by multiple passages through tissue culture. It is still live virus, but has been attenuated so it is no longer capable of causing the disease.
Advantages are it is more potent, requiring no adjuvant. Reversion to the virulent state via mutation is possible, however. Thus, some viruses are not suitable for this process, such as rabies and feline leukemia.
MLV vaccines also present way more antigen to the patient than is necessary.
Thus, the clever evolution of the newest, latest and greatest DNA recombinant r-DNA viral vectored technology. It’s not really quite as complicated as it sounds.
Let’s use feline leukemia virus as an example. Researchers have determined there are only two specific viral proteins required to induce immunity in the cat. Inclusion of all the other leukemia virus proteins in the vaccine is unnecessary.
The leukemia virus’ DNA for these two antigens is incorporated by genetic splicing into the DNA of a non-pathogenic virus. In this case, the canary pox virus is used because it cannot replicate nor cause disease in mammals. This DNA-altered, live pox virus is then injected into the cat, carries the leukemia virus DNA into the cat’s lymphocytes and induces antibody production to protect against feline leukemia virus.
The irony here is Tweety Bird unknowingly steps forward to rescue Sylvester!
This technology provides many advantages. There is no potential for reversion to virulence because no whole leukemia virus is included. There is no adjuvant additive. There is minimal antigenic challenge only those proteins necessary for immune stimulation are included and only one-fourth the volume of previous vaccines is required.
This causes less stress on the immune system and less likelihood for autoimmune or other adverse reactions.
To date, r-DNA canary pox virus vectored vaccine technology is available for feline leukemia, rabies, canine distemper, corona and parvovirus and borrelia (lyme disease.) It is also used in equine influenza and West Nile vaccine. It is currently being studied in developing an HIV-1 vaccine.
Vaccine technology has made giant strides and is helping to relieve the anxiety of choosing whether to vaccinate. Safety and efficacy have been maximized, and adverse effects minimized.
Discuss the options with your veterinarian. An appropriately individualized vaccine protocol can be outlined for your pet’s specific needs.