EMERGING TRENDS IN VACCINATIONS: 2008 UPDATE
INTRODUCTION: In 2006 AAHA (American Animal Hospital Association) published a revision of its 2003 Canine Vaccine
Guidelines for veterinarians based on the result of the Canine Vaccine Task Force's 2005 report. Since then several
of the nation's veterinary schools have revised their own recommended protocols for vaccinating pets. And at a
recent ACVIM (American College of Veterinary Internal Medicine) Forum held on June 2008, Richard Ford, DVM, MS,
DACVIM, DACVPM (Hon), a recognized leader in this field, presented material on both recommendations for small animal
vaccinations and adverse reactions to vaccines. This was a follow-up to his 2005 report to the World Small Animal
Veterinary Association (WSAVA) outlining risk: benefit analyses of various vaccination protocols.
The below is a synopsis of these newer recommendations with a commentary on what practical concerns for the dog
owner may have been changed, along with Dr. Ford's own current recommendations to veterinarians from his online
Vaccines & Vaccinations guidelines. I've also included a summary of current recommendations for core vs. non-core
and non-recommended vaccinations for dogs based on risk category and issues of exposure, and some data on various
types of vaccinations, which will likely affect future trends in vaccinating our pets. The first portion of this
article provides the practical information most dog owners want to have about vaccinations and ends with a chart
of current recommendations. The second part of the article is more detail-oriented, and offers some information
and comments from expert sources on various aspects of recommended vaccination protocols. There is a reference
section at the end of the article which provides even more detailed (and lengthy) resources on the current state
of, and emerging trends in small animal vaccination protocols. This article's organization hopefully spares the
reader looking for immediate and practical data from having to look too far, while providing the student of animal
husbandry a chance to review the material in depth.
SECTION ONE: In many significant ways the recent updates to the 2001 AVMA and 2003 AAHA vaccination guidelines
follow earlier changes to policy, such as outlining a set of "core" versus "non-core" vaccinations,
recommending at least core vaccinations for puppies every 3-4 weeks between 2 and 4 months, and recommending adult
dogs be vaccinated every three years. The single largest change in the recommendations in fact doesn't affect the
average pet owner, as the 2006 version includes for the first time a set of specific recommendations for shelters.
There is a newly revised section on vaccine licensing procedures (to include the legal ramifications of vaccines),
and an updated section concerned with reporting adverse vaccine reactions and with the licensing of conditional
vaccinations. There is a section updating new information on serologic testing (i.e. titer tests). Also given in
the 2006 update is new information about recombinant type vaccines, such a live-vectored and subunit vaccines.
(And given the pace of vaccine technology, it can be anticipated future updates may well be generated based on
new developments in this field.) The AAHA report again emphasizes the attending veterinarian make specific decisions
when vaccinating small animals that are focused on the individual patient's risk: benefit analysis, which has been
the stated policy also of the American Veterinary Medical Association (AVMA) for at least the past decade.
So, as far as the average dog owner is concerned, on a practical level little has changed in what are the recommended
procedures for vaccinating your dogs, assuming your own attending veterinarian has been keeping up with the protocols
established by these national-level professional veterinary associations. There is still a set of core vaccinations
recommended, with puppies to receive the standard DA2P every 3-4 weeks (beginning at 6-8 weeks) until at least
16 weeks of age, then a "booster" at a year, and then vaccinated every three years afterwards. The new
guidelines specifically advocate a 3 year (as to opposed to annual) cycle of standard vaccinations, based on emerging
data on the extended duration of immunity for these core vaccines. The emphasis on a puppy receiving its last DA2P
at four months is new, and is based on reports of vaccinated puppies not having a protective titer when their last
vaccine was given at 12 weeks. Note there is no national recommendation for rabies: rabies vaccinations are to
be administered per local and state laws (typically first vaccination given at 3-6 months, with a general recommendation
of a "booster" at a year, then every year or every 3rd year, depending upon the laws). These are the
only recommended core vaccines. Non-core vaccines are a separate category from non-recommended vaccines, and constitute
a group of vaccines some dogs will need at some times, depending on an assessment of the individual animal's risk:
benefit analysis. These include vaccines for "kennel cough," "lepto," Lyme disease, snake bite
and periodontal disease. Non-recommended vaccines include that for "corona," Giardia, CAV-2 killed, CAV-1
vaccines, and some other "special circumstance" recommendations. The following 2008 chart provides an
outline of core and non-core vaccinations for dogs, with vaccination recommendations as made by Dr. Ford.
FOR RECOMMENDED CANINE VACCINES, SEE THIS CHART:
http://www.dvmvac.com/CVacs1.shtml
SECTION TWO: The rest of this article deals with various aspects of vaccination protocols, most particularly
those that are newly emerging, controversial and/or confined to particular dogs with an altered risk: benefit analysis.
It is probably best to start with some common sense guidelines when embarking on the task of reading a lot of technical
material outside one's own field. With the issue of vaccinations, I feel it is important to keep in mind that vaccine
protocols are always based on a consensus between involved parties and so a matter of (hopefully good) judgment.
On a broad scale this means a consensus about general vaccine practices amongst professional veterinary organizations,
and the good judgment of your attending veterinarian as to how these national guidelines need to be applied in
your area. On a personal level this means a consensus between you and your vet judging what the best set of choices
is for each of your own individual animals. As the AAHA Guidelines state: "Immunization [is] categorized as
a medical procedure with definite benefits and risks, and one that should be undertaken only with individualization
of vaccine choices and after input from the client."
For most dogs most of the time the nationally established protocols for pets as outlined above are going to serve
as a good guideline to balance the risks of disease against the potential risks (or simple waste of resources)
when vaccinating. Where there are choices to be made (such as in the non-core area of vaccines, or two vaccines
that are both on the recommended list), probably all choices given are generally reasonable, so to choose then
will require you to understand the options as they apply to your region and perhaps personal needs. There some
circumstances however where you might need to consider more vaccines as the wisest course, and other situations
where less than the generally recommended protocol appears desirable.
The newly developed protocols for shelter dogs outline an aggressive vaccination policy (with more vaccines given
more often essentially), and given the transitory nature of the population in a shelter combined with the unknowns
about the background of the dogs entering the typical shelter this makes sense for this population as a rule, just
as much as it seems unnecessary for the average pet or show dog to be vaccinated with "everything" annually,
or the typical puppy to get vaccinations every 2 weeks from 5-6 weeks onward, etc. However there are arguably at
least some purebred rescue, even show and working dog scenarios where this more aggressive vaccine policy might
be in order. The guidelines developed for the shelter scenario might for example apply to some of our Dane rescues,
larger boarding or show/handling kennels: for example when and where many dogs come and go to many other places,
and where puppies of various ages are present, and/or where disease is present, as these are the sorts of circumstances
for which the shelter protocols were developed. Even in smaller kennel situations, when your dogs may have been
exposed to actual disease, they, like orphan pups (in any situation) may well benefit from a vaccine schedule that
is revised, and sometimes revised "up" in the sense of a more aggressive protocol. So reviewing the recommendations
for shelters may be useful, as the protocols developed here may have a wider application beyond the shelter situation.
Consultation, consensus and clear judgment here are key factors to a best-fit outcome.
Just as there may be times it can be argued that more vaccines are warranted, there are certainly times "less
is more." So-called "at risk" populations are an example: typical "at risk" populations
are the very old, the very young, dogs that are ill, diseased or pregnant. Such individuals typically need to have
the entirety of their animal husbandry practices carefully tailored to their particular needs, and this would include
a long look at how and when they will be vaccinated. Here each case will have to be individually addressed: for
a dog with a minor illness and at high risk for serious infectious disease that vaccines can prevent, the answer
will be different than the dog dangerously or even chronically ill with little or no risk of being exposed to something
like "parvo." If you have a dog with a systemic autoimmune disease like "lupus" (SLE), or other
immune disorder, you will want to carefully craft a vaccination regime to minimize the increased risk of adverse
immune reaction associated with such disease. At risk animals need to be protected by prevailing herd immunity
in that they cannot necessarily mount an effective defense to infectious disease (i.e. they are non-responders).
As a reminder, herd immunity is the effect of protecting the vulnerable amongst us by insuring a pathogen cannot
effectively penetrate the greater population (which is largely immunized against the potential invader). As herd
immunity drops, the risk of infection for all, but especially the vulnerable, rises.
A strategy of limiting vaccinations may also be needed in families known to have "vaccine reactions"
of various kinds; here is at least a case to tailor vaccine use to the dog's practical needs and also consider
the use of titers in lieu of simply "boostering" the dog. Serologic (titer) testing has its limitations,
but can be useful if these limits are understood. Titer testing was used, for example, to establish that the many
puppies contracting canine distemper virus (CDV) in various shelters nation-wide recently (e.g. Chicago, Los Angeles)
lacked a protective titer, while those resistant to infection had mounted a measurable antibody titer to distemper.
The AAHA Guidelines seems to encourage titer testing puppies at the end of their first series of vaccinations,
stating: "titer testing is the only way to ensure that a puppy has developed an immune response after vaccination,"
and suggests titer testing may also aid in determining when to begin vaccinating (by defining the advent of that
"window of susceptibility" where maternal antibodies have fallen low enough the puppy can be actively
immunized). So if there a question in your mind about a dog's immune "status" (whatever his age), discuss
titer testing as an option with your attending veterinarian.
Bear in mind titer testing using enzyme immunoassays (ELISA) and immunofluorescence assay (IFA) style titers are
not generally recommended for all they are commonly used, as the "gold standard" for titer testing is
either virus neutralization (VN) such as is used for CDV or hemagglutination inhibition (HI) currently available
to test for antibody to CPV-2. With titer testing, the amount of error has to be assumed to be four-fold, so it
pays to pay for the better sort of test (sent to the better sort of referral laboratory), and then to read them
conservatively (a value, for example of 5 or more, being defined as positive) for best results. There is now an
in-house test for CDV and CPV-2 approved by the USDA in 2005 (TiterChek by Synbiotic); this allows more access
to a quick and affordable titer testing option. But this is an ELISA test, not the preferred VN or HI style test,
so should be used more as a screening test than when a definitive answer is needed. The AAHA Guidelines does offer
the clinical veterinarian a specific protocol to follow as to titer testing where a vaccine failure is a concern.
As field tests have established up to 15-20% of our dogs will lack a protective titer to either CDV or CPV-2, herd
immunity does seem at stake, and as we have all experienced at some point what can occur when disease breaks out,
for the sake of general dog population as well as the prevention of disease in our own personal pets, ensuring
a protective titer is created in those dogs able to respond in an immunologically normal way is certainly warranted.
Ensuring a protective titer exists isn't limited to the use of titer testing, but rather typically includes vaccinations;
and good animal husbandry practices, such as isolating exposed and at-risk dogs as well as clinically ill individuals,
need be employed as well. It cannot be forgotten a loss of herd immunity means an opportunity for the outbreak
of infectious disease, and in the case of disease with high morbidity and mortality rates, animals exposed can
not only fall ill and spread disease, but can also offer the pathogen an opportunity to gain in virulence. Herd
immunity protects us all, as when the bulk of the population does mount an effective titer, those individuals too
fragile to do so are protected (vs. threatened) by the animals that surround them. This simple principle of biology
predates any program of vaccination, but certainly applies to situations where vaccines can prevent an outbreak
of virulent disease. And applied to today's world, as unpleasant as it is to have to point out, the same principle
suggests those opting out of vaccines entirely are potentially putting the rest of us at risk as was recently discussed
in Time magazine article entitled "How Safe Are Vaccines?". We have to balance the needs of our loved
ones against the needs of the general population in making vaccine decisions, as what occurs "out there"
is likely to come home to haunt us all later.
A word on new vaccine technologies before I close: the majority of vaccines available for dogs currently are either
"modified live" (i.e. attenuated) or "killed" (i.e. inactivated) vaccines. Just now appearing
on the horizon are some new categories of vaccines that are the result of advances in understanding of disease
pathogenesis (how a virus or bacteria makes our dogs sick) at the molecular and genetic level. These advances are
beginning to change the way we can vaccinate, and are, along with advances in adjuvant use (the portion of an inactivated
vaccine that stimulate the immune system to produce a titer), already producing some new products on the market.
These products are right now so very new there is very little field data on them; however in theory they ought
to produce good or better protection with less risk to the individual animal, so may well prove both safer and
more efficacious. It is axiomatic that with newer technologies may come many solutions, like that to the inherent
conflict between the needs of the individual and the needs of the community when it comes to vaccines. New vaccines
may provide safer alternatives for all, and new lines of research may lead to screening tests for the genetic contributions
associated with immune disorders that underlie much of what constitutes adverse vaccine reaction. Such advances
may end in both the vulnerable individual and the community s/he interacts with receiving equal consideration.
For now that's just a dreamy cloud formation on the horizon, but an outline of these newly emerging forms of vaccines
(with a few brief comments as to how they currently apply to our dogs) is given below.
Live Vectored Vaccines: A live vectored vaccine is one in which specific genes from the target pathogen are inserted
into an innocuous host organism, so that a protective titer can be mounted without any chance of disease. Another
potential boon of such "recombinant" vaccines is the ability to break through what is called passive
acquired maternal antibody (PAMA), thus immunizing puppies in that terrible "window of susceptibility"
where the amount of PAMA they have blocks the vaccination but does not provide effective protection against disease.
Currently there is a live vectored vaccine for CDV and there is unpublished data to suggest this new rCDV recombinant
vaccine (Recombitek Canine Distemper, Merial) can effectively immunize puppies where maternal antibodies are an
issue. Recently Ron Schultz reviewed this vaccine favorably, as has Richard Ford. There is even a comment by Ford
that this vaccine is to be preferred in Weimaraners prone to hypertrophic osteodystrophy (HOD) as that is considered
to be a immune-mediated disease in that breed. The rCDV vaccine can also be administered as early as 3 weeks to
puppies at high risk of disease. The idea here is that this sort of vaccine is highly effective as well as has
a low incidence of undesirable immunological reaction because the host (the dog)'s immune system doesn't recognize
the canary pox that is the vector used to delivery the needed CDV genes.
Subunit Vaccines: Subunit vaccines are another strategy to lower the potential for adverse vaccine reaction while
maintaining efficacy. They simply contain a portion of the offending organism, a part expected to still result
in a proper titer, so are a sort of "purified" vaccine if you will, as much of the extraneous protein
(likely to cause an immune reaction) is gone. They can also be highly cost efficient as making large amounts of
such purified protein is economical. The downside to subunit vaccines is that if the portion chosen is not all
that is needed for the animal in question to mount a titer, well, then the vaccinated animal will still end up
in the vaccine failure category. (Here is a place for titer testing?) There is a subunit vaccine for Lyme disease
called OspA (rLyme Recombitek, Merial), and given the controversial status of Lyme disease vaccinations, its efficacy
is probably worth exploring for those in high risk areas such as New England. There is also a subunit vaccine available
against four serovars of leptospirosis (Duramune Leptospirosis, Fort Dodge). Again, if there is a need to vaccinate
against "lepto" then the subunit vaccine will greatly reduce adverse vaccine reactions, which appear
to occur more often with bacterin-based vaccines like those traditionally made to fight the deadly and zoonotic
disease leptospirosis.
Gene-deleted Vaccines: Gene-deleted vaccines are, as the name implies, vaccines made from a pathogen that has lost
(or had inactivated) a portion of its genetic code. This is somewhat like making an attenuated (modified live)
vaccine, but doing it at the DNA level: the idea is the virus, for example, loses its virulence and ability to
convert (to virulence), but the vaccinated host still is able to mount an effective immune response upon challenge
to the wild type (virulent) pathogen. A potential benefit of gene-deleted vaccines is the ability to tell the vaccinated
animal from the naturally infected animal, which is currently impossible with such as "modified live"
vaccines. There are no current gene-deleted vaccines for dogs.
DNA Vaccines: DNA vaccines are probably the most difficult to describe in short order, but suffice to say a specific
portion of the pathogen's DNA (useful in mounting a titer in the target host) is inserted into a (literally) free-wheeling
"donut" of DNA called a plasmid that bacteria can harbor. Then the little plasmid is extracted and purified
and (using various methods) is inserted into the host. These are the so-called "naked" DNA vaccines,
and have many potential benefits (from affordability, stability and overcoming PAMA to increased duration of immunity
and reduced potential for virulence). There is a newly licensed DNA vaccine for West Nile Virus in horses, but
no such "animal" yet is available to dog.
SUMMARY: For all this is a time where there is much new and emerging information on vaccines and vaccination protocols,
the current recommendations for vaccinating our dogs should still seem very familiar to most of us. In general
right now all that is needed for most of us is to use a conservative vaccination program that emphasizes vaccinating
against the most serious diseases in general, and then includes for consideration those diseases your own dogs
may be at greater risk for than the general population (by virtue of location, age, activities, etc.). A personalized
program should then be developed for each animal at different life stages, and these new recombinant vaccines should
be considered for their added safety where available (and probably can be expected to largely replace older styles
of vaccines over time). Complacency and convenience should not be driving factors in a vaccine program, and "well
pet" visits (at least annually) should replace annual vaccinations as a general rule. Also it is important
to ensure that puppies acquire a protective titer and so mount an appropriate immune response, so titer testing
may be useful at times, and it may be more appropriate to titer older animals as well as various "at risk"
individuals.
We should all likely keep an eye on the new developments in vaccine technology, as well as work closely with an
able and trusted veterinarian to develop a suitable vaccine protocol for our own individual animals. Given recent
history (from the advent of canine influenza to recent reports of distemper and parvovirus being endemic to certain
populations), we also need to keep a watchful eye on the potential for outbreaks of disease. In practical terms
this means for most of us giving puppies standard, minimal vaccinations at 8, 12 and 16 weeks, for example, and
after giving them dogs a "booster" at around a year of age, then planning for a 3 year interval for core
vaccines (with annual non-core) as recommended by both national veterinary organizations and most veterinary colleges.
Protecting our animals also means taking a conservative course when the potential for contagion in present, and
committing to such good animal husbandry as proper hygiene and isolation when we find our own animals may have
been/be exposed to infectious disease, and/or are potentially contagious. (For example staying home from shows
when a local outbreak of disease occurs on the circuit or within our own kennel.) As Ford has noted: "the
benefits of vaccination, when performed in accordance with currently published recommendations far outweigh the
risk of vaccine-induced illness or disease." But it cannot be overemphasized that the decisions made about
vaccinations should be done in consensus with the attending veterinarian and always with the informed consent of
the owner. This means most of us will need to learn a bit more about the choices in vaccines to be able to truly
give informed consent, but most of all implies we will all have to employ good judgment and use common sense in
making what are essentially judgment calls.
JP Yousha. 30 June 2008.
References:
2006 AAHA Canine Vaccine Guidelines, Revised (online reference):
http://www.aahanet.org/PublicDocuments/VaccineGuidelines06Revised.pdf
2003 AAHA Canine Vaccine Guidelines (historical document):
http://www.chromadane.com/avmavx.htm
American College of Veterinary Internal Medicine (ACVIM) Forum:
http://www.ACVIMForum.org
AKC Breeder: Vaccinations: Know What You Are Doing (online article):
http://www.akc.org/enewsletter/akc_breeder/2005/summer/vaccinations.cfm
Canine Distemper & Vaccination (online reference):
http://ph.merial.com/pet_owners/pdf/news_shcultz.pdf
Canine Leptospirosis: Current Issues on Infection and Vaccination:
http://www.labbies.com/lepto.htm
Core and Non-Core Canine Vaccines and Administration Recommendations:
http://www.dvmvac.com/CVacs1.shtml
DVM News Magazine (online reference):
http://www.dvmnews.com/
Hot Topics (for veterinarians, concerning vaccination guidelines):
http://www.dvmvac.com/HotTopic.shtml
How Safe Are Vaccines? By Alice Park. TIME magazine: June 2, 2008: pp 36-41.
Types of Vaccines Licensed For Dogs and Minimum Duration of Immunity:
http://www.dvmvac.com/CVTypes.shtml
Infectious Disease Prevention Changes In The Wind (by RB Ford):
http://www.vin.com/VINDBPub/SearchPB/Proceedings/PR05000/PR00201.htm
Leptospirosis Vaccination Fact Sheet:
http://www.vetmed.wsu.edu/rdvm/lepto.asp
UC Davis VMTH Canine and Feline Vaccination Guidelines (Revised 12/07): http://www.vmth.ucdavis.edu/vmth/clientinfo/info/genmed/vaccinproto.html
Vaccine Protocols Discussed at 2008 ACVIM Forum:
http://www.goodnewsforpets.com/Articles.asp?ID=1129
WSU College of Veterinary Medicine: Community Practice Vaccination Protocols: April 2008:
http://www.vetmed.wsu.edu/depts-vth/vaccinations.aspx