Sunday, November 20, 2011

2011 AAHA Vaccine Guidelines - The Reader's Digest Version

Determining an appropriate vaccination regimen for your dog(s) is in some respects similar to drinking alcohol responsibly at a really fun party. At the party you want to drink enough to have the desired effect, but not so much that you suffer adverse effects such as a DUI conviction or nasty hangover. To achieve those sometimes conflicting goals one must determine what to drink and how often to refill the glass or mug.

When vaccinating dogs one must determine what vaccines to administer and how frequently to administer them to provide adequate protection against the target diseases while avoiding adverse effects that can have a huge impact on your dog’s health and longevity.

As with alcohol there are factions with extreme philosophical views on opposite ends of the spectrum. Like adamant teetotalers, some believe that all vaccines are akin to deathly poison and should never be administered to dogs. At the other extreme are owners and some veterinarians who believe that if a little is good, a lot must be better and advocate vaccinating far more frequently than is required.

Like the partier, most of us are seeking the middle ground that provides adequate protection against preventable diseases while avoiding adverse events that have been associated with canine vaccines. A few days ago one of my Facebook friends posted that the American Animal Hospital Association recently released their updated 2011 AAHA Canine Vaccination Guidelines. Based on the best currently available scientific knowledge, the AAHA Canine Vaccination Guidelines offer a well reasoned middle ground that you and your veterinarian can use to develop an appropriate regimen for your particular circumstances.

The Core Vaccines:

There are only four “core” vaccines recommended for all dogs, regardless of their home location or status as companion, sporting, or working animal. These four are vaccines against canine parvovirus, canine distemper, canine adenovirus and rabies.

Three of the four core vaccines (the rabies vax is the exception) are ‘infectious vaccines’ which must infect the host’s cells to immunize. Infectious vaccines are more effective than noninfectious types because they provide the same types of cellular, humoral, systemic and local immunity that are produced by natural exposure, but the vaccine organisms are attenuated and will not cause the disease.

Because they are so effective, the AAHA guidelines acknowledge that a single dose will prime, immunize and boost the dog’s immune response to disease-causing organism unless maternally derived antibodies (from mother’s milk) interferes. Infectious vaccines provide immunity for many years, perhaps even for the lifetime of the dog.

Like most of the non-core vaccines, the rabies vax is a noninfectious (inactivated or killed) vaccine. These vaccines do not infect the host to produce new antigens, and therefore must contain adequate amounts of antigen to immunize. Additionally, many of the non-infectious must also contain adjuvants, a wide variety of substances that maintain or deposit the antigen into tissues to promote a more robust immune response. Some adjuvants, such as aluminum salts, are inorganic and others such as some oils are organic. Although not permitted in human vaccine, oil based adjuvants are common in veterinary products.

Many veterinarians consider noninfectious vaccines to be the safest because the virus or bacteria is dead. It can not possibly revert to virulence or cause the disease the vaccine was intended to prevent. On the other hand, hypersensitivity reactions and apparently other adverse effects are more commonly reported after vaccination with noninfectious products, perhaps due to the higher concentration of antigen, the presence of potentially toxic adjuvant, or a combination of both.

Because noninfectious vaccines do not actually infect the animal, the immunity they provide is more short lived than that of infectious vaccines, thus they need to be ‘boosted’ from time to time to provide protection.

Deciding Which Vaccines to Administer:

I believe one of the most important things the 2011 Guidelines provide is a firm statement against over-vaccination of dogs, especially on page 33 regarding adverse reactions to vaccines. “Vaccines are biologic products; administration should be tailored to the needs of the individual dog and should never be given needlessly. All vaccines have the potential to cause adverse reactions following administration.”

As noted earlier, there are four vaccines that are considered vital for all dogs in the United States and Canada, regardless of where they live or their life circumstances. These four vaccines are against parvovirus, canine adenovirus, canine distemper and rabies. Rabies is such a frightening public health concern that all 50 States have laws requiring that dogs be vaccinated against the disease, sometimes far more frequently than is healthy for the dog.

Noncore vaccines can be considered ‘optional’, and the decision to use or not use the products should be based on a variety of factors. For example, the prevalence of a particular disease in your area, whether or not your dog(s) may interact or be exposed to other dogs that may carry and transmit the diseases, how well your dog may be able to fight off a vaccine preventable disease if the wrong decision is made, and so forth. It is HIGHLY recommended that you consult with your veterinarian before adopting a particular vaccination regimen.

At least 1 commonly administered canine vaccine is not recommended at all. That is vaccine against canine coronavirus. Neither type of coronavirus vaccine on the market has been show to reduce the disease. In other words, it just doesn’t work well.

Vaccines against Lyme disease, Leptospirosis, and Western Diamondback rattlesnake venom are recommended only for dogs living in or visiting regions where the risk is significant. The decision to vaccinate against Bordetalla bronchiseptica (one of many causes of kennel cough) is also based on the risk of exposure.

Deciding When to Vaccinate:

The decision on when to vaccinate is most critical when dealing with puppies. During the first few weeks of life, puppies enjoy the protection of maternally derived antibodies which they receive from their mother’s milk (specifically, from colostrum). When the puppy is weaned the level of those maternally derived antibodies starts dropping, but the loss of immunity is not instantaneous.

Those maternally derived antibodies do a great job of protecting the puppy from disease, especially if the dam was properly immunized. The problem is that so long as the MDA are active, they will attack an infectious (core) vaccine just as readily as they attack naturally acquired pathogens. Attempting to vaccinate a puppy at too young an age is an exercise in futility, a waste of money and an unnecessary exposure to risk.

Anecdotal observations seem to indicate that too early vaccination carries an increased risk of vaccine related adverse events, and that some ‘primitive’ breeds of dogs including our ‘village’ or ‘trap-line’ types of huskies are particularly susceptible.

On the other hand, waiting too long can leave the puppy vulnerable to potentially fatal diseases. This can easily occur when puppies are orphaned, weaned early or for some other reason do not receive adequate MDA.

Since it isn’t practical (nor inexpensive) to measure MDA in every single puppy, the AAHA guidelines recommend administering the infectious core at 8, 12 and 16 weeks of age. Under this regimen puppies with inadequate MDA are immunized as soon as their systems are mature enough to respond, and late enough to ensure that puppies from dams with exceptionally strong immunize systems are also covered.

Following the puppy series, Table 1 of the Guidelines recommends that puppies completing the initial vaccination series by 16 weeks of age or younger should receive a single booster vaccination no later than 1 year of completion of the puppy series, and be revaccinated at three or more year intervals afterward. Since the text of the guidelines on page 13 notes that the duration of immunity from infectious vaccines extends from 5 years up to the life of the dog, it may be quite reasonable to hold off a year or two or to run ‘titer tests’ before revaccinating. We’ll address titer testing later in the article.

Because the noncore vaccines are noninfectious, they don’t have nearly so long duration of immunity as the infectious core vaccines. The recommended schedule of administration of the noncore vaccines varies somewhat, but are included in the AAHA Canine Vaccine Guidelines for easy reference.

Rabies - The Red-headed Step Child of Vaccines:

Being reasonably politically astute, the AAHA was apparently careful to avoid any recommendation that might run afoul of the laws of any jurisdiction. In my opinion, that is rather unfortunate as the legal requirements of some jurisdictions do not seem to be based on any sort of scientific fact but are instead founded on fear. That’s unfortunate because the rabies vaccine has been implicated in more adverse events than any other product. Although there is good evidence to show that rabies vaccines currently on the market have a duration of immunity of at least 5 years (which has been proved in France) and likely greater than 7 years, all 50 United States require at least a 3 year revaccination schedule, and many local jurisdictions require annual revaccination, even if a licensed 3-year vaccine is given.

Alaska’s State requirement is defined in title 7 of the Alaska Administrative Code. 7ACC27.020 (b)(3) reads; “rabies vaccination of dogs and cats is required in accordance with schedules in the Compendium of Animal Rabies Prevention and Control, 2002, as adopted in (1) of this subsection; evidence of such a vaccination is to be recorded on the Standard Vaccination Certificate specified in (2) of this subsection; at the time of vaccination, the owner or keeper of a dog vaccinated must be given a metal tag bearing a number and the year the vaccination was given that is recorded on the Standard Vaccination Certificate; the tag must be affixed by the owner or keeper to a collar or harness and must be worn by the dog for which the certificate is issued except that the dog need not wear the tag while harnessed in a dog team or while participating in organized training or competition;”

The CDC’s Compendium of Animal Rabies Prevention and Control calls for the vaccination of dogs at 3 months (12 weeks) of age, with a second dose administered within a year of the first. Afterward, a three year schedule can be followed when using an appropriately licensed 3-year vaccine.

If you live in a State other than Alaska I’d suggest you research the law applicable to the jurisdiction in which you reside.

Titer Testing:

The 2011 AAHA Guidelines offer some good information on serologic testing, commonly called “titer testing” as a means of determining and monitoring immunity. There have been significant strides in serologic over the past few years, making the tests more readily available and less expensive, though they are usually more expensive than vaccination. Today most (perhaps all) laboratories have qualified and standardized their methodologies with samples that were tested by “gold standard” methods, to ensure accuracy. There are also two quick in-clinic tests that provide a positive or negative result that have been approved by the USDA.

Serologic tests run 2 weeks or more after vaccination can be used to determine whether or not the vaccine elicited an immune system response. If the dog does not have antibodies, it can be revaccinated with a different product. Titer testing can also be used to determine whether or not a dog needs to be revaccinated after a number of years have passed since his or her last vaccination. It the titer test is positive, there is no reason to revaccinate the dog and subject him to potential adverse effects.

It should be noted that the AAHA states that the concerns some have expressed about the variability in titers among serologic tests have little or no validity when applies to protection from distemper, parvovirus, adenovirus and rabies.  Nonetheless, titer tests for rabies can not legally be used in lieu of vaccination. If the rabies vaccination is not current and dog bites someone, the dog must be treated as though s/he were unvaccinated and quarantined. In some cases the dog might even be impounded or even euthanized.

Other Factors that Impact Vaccination Decisions:

Mushers who participate in races, formally organized runs and similar events may have to consider another issue when making their vaccination decisions. The rules of some races, including the Iditarod Trail Sled Dog Race, require more frequent vaccination. For example, Iditarod rule number 40 states that all dogs running the race must have received vaccination against distemper, hepatitis (from which protection is derived from the canine adenovirus 2 vaccine), lepto (a noncore vaccine against an organism that can’t survive freezing temperatures)and parvo between April 1, 2011 and February 18, 2012. As a consequence many long distance racing dogs are put on a de-facto annual schedule of vaccination, in spite of the AAHA recommendations. The RGO (race giving organization) provides no rationale to support the rule that apparently requires excessive vaccination of a fair number of dogs.

Winding down…

The 2011 AAHA Canine Vaccination Guidelines have evolved somewhat since the 2006 Guidelines were released.  My impression is that they provide more information about the available vaccines, risks and types of adverse events that can result from vaccination, support the use of serological testing as a tool for making informed vaccination decisions and lays some groundwork to support a more reasonable schedule of rabies vaccination should the current rabies challenge study prove that rabies vaccines provide a longer duration of immunity than that for which they are currently licensed.

As I noted earlier, the AAHA Guidelines seem to represent a reasonable, scientifically supported middle-of-the-road approach that weighs the risk of disease against the potential adverse effects of over-vaccination.  I highly recommend all dog owners, especially those accustomed to vaccinating their own dogs, download and become familiar with the guidelines.

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