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Vaccine Protocol
The challenge to produce effective and safe vaccines for the prevalent
infectious diseases of humans and animals has become increasingly
difficult. In veterinary medicine, evidence implicating vaccines in
triggering immune-mediated and other chronic disorders (vaccinosis) is
compelling. While some of these problems have been traced to
contaminated or poorly attenuated batches of vaccine that revert to
virulence, others apparently reflect the host's genetic predisposition
to react adversely upon receiving the single (monovalent) or multiple
antigen "combo" (polyvalent) products given routinely to animals.
Animals of certain susceptible breeds or families appear to be at
increased risk for severe and lingering adverse reactions to vaccines.
The
onset of adverse reactions to conventional vaccinations (or other
inciting drugs, chemicals, or infectious agents) can be an immediate
hypersensitivity or anaphylactic reaction, or can occur acutely (24-48
hours afterwards), or later on (10-45 days) in a delayed type immune
response often caused by immune-complex formation. Typical signs of
adverse immune reactions include fever, stiffness, sore joints and
abdominal tenderness, susceptibility to infections, central and
peripheral nervous system disorders or inflammation, collapse with
autoagglutinated red blood cells and jaundice, or generalized pinpoint
hemorrhages or bruises. Liver enzymes may be markedly elevated, and
liver or kidney failure may accompany bone marrow suppression.
Furthermore, recent vaccination of genetically susceptible breeds has
been associated with transient seizures in puppies and adult dogs, as
well as a variety of autoimmune diseases including those affecting the
blood, endocrine organs, joints, skin and mucosa, central nervous
system, eyes, muscles, liver, kidneys, and bowel. It is postulated that
an underlying genetic predisposition to these conditions places other
littermates and close relatives at increased risk. Vaccination of pet
and research dogs with polyvalent vaccines containing rabies virus or
rabies vaccine alone was recently shown to induce production of
antithyroglobulin autoantibodies, a provocative and important finding
with implications for the subsequent development of hypothyroidism
(Scott-Moncrieff et al, 2002).
Vaccination also can overwhelm
the immunocompromised or even healthy host that is repeatedly
challenged with other environmental stimuli and is genetically
predisposed to react adversely upon viral exposure. The recently weaned
young puppy or kitten entering a new environment is at greater risk
here, as its relatively immature immune system can be temporarily or
more permanently harmed. Consequences in later life may be the
increased susceptibility to chronic debilitating diseases.
As
combination vaccines contain antigens other than those of the
clinically important infectious disease agents, some may be
unnecessary; and their use may increase the risk of adverse reactions.
With the exception of a recently introduced mutivalent Leptospira spp.
vaccine, the other leptospirosis vaccines afford little protection
against the clinically important fields strains of leptospirosis, and
the antibodies they elicit typically last only a few months. Other
vaccines, such as for Lyme disease, may not be needed, because the
disease is limited to certain geographical areas. Annual revaccination
for rabies is required by some states even though there are USDA
licensed rabies vaccine with a 3-year duration. Thus, the overall
risk-benefit ratio of using certain vaccines or multiple antigen
vaccines given simultaneously and repeatedly should be reexamined. It
must be recognized, however, that we have the luxury of asking such
questions today only because the risk of disease has been effectively
reduced by the widespread use of vaccination programs.
Given
this troublesome situation, what are the experts saying about these
issues? In 1995, a landmark review commentary focused the attention of
the veterinary profession on the advisability of current vaccine
practices. Are we overvaccinating companion animals, and if so, what is
the appropriate periodicity of booster vaccines? Discussion of this
provocative topic has generally lead to other questions about the
duration of immunity conferred by the currently licensed vaccine
components.
In response to questions posed in the first part
of this article, veterinary vaccinologists have recommended new
protocols for dogs and cats. These include: 1) giving the puppy or
kitten vaccine series followed by a booster at one year of age; 2)
administering further boosters in a combination vaccine every three
years or as split components alternating every other year until; 3) the
pet reaches geriatric age, at which time booster vaccination is likely
to be unnecessary and may be unadvisable for those with aging or
immunologic disorders. In the intervening years between booster
vaccinations, and in the case of geriatric pets, circulating humoral
immunity can be evaluated by measuring serum vaccine antibody titers as
an indication of the presence of Aimmune memory@. Titers do not
distinguish between immunity generated by vaccination and/or exposure
to the disease, although the magnitude of immunity produced just by
vaccination is usually lower (see Tables).
Except where
vaccination is required by law, all animals, but especially those dogs
or close relatives that previously experienced an adverse reaction to
vaccination can have serum antibody titers measured annually instead of
revaccination. If adequate titers are found, the animal should not need
revaccination until some future date. Rechecking antibody titers can be
performed annually, thereafter, or can be offered as an alternative to
pet owners who prefer not to follow the conventional practice of annual
boosters. Reliable serologic vaccine titering is available from several
university and commercial laboratories and the cost is reasonable.
Relatively
little has been published about the duration of immunity following
vaccination, although new data are beginning to appear for both dogs
and cats.
Our recent study (Twark and Dodds, 2000), evaluated
1441 dogs for CPV antibody titer and 1379 dogs for CDV antibody titer.
Of these, 95.1 % were judged to have adequate CPV titers, and nearly
all (97.6 %) had adequate CDV titers. Vaccine histories were available
for 444 dogs (CPV) and 433 dogs (CDV). Only 43 dogs had been vaccinated
within the previous year, with the majority of dogs (268 or 60%) having
received a booster vaccination 1-2 years beforehand. On the basis of
our data, we concluded that annual revaccination is unnecessary.
Similar findings and conclusions have been published recently for dogs
in New Zealand (Kyle et al, 2002), and cats (Scott and Geissinger,
1999; Lappin et al, 2002).
When an adequate immune memory has
already been established, there is little reason to introduce
unnecessary antigen, adjuvant, and preservatives by administering
booster vaccines. By titering annually, one can assess whether a given
animal's humoral immune response has fallen below levels of adequate
immune memory. In that event, an appropriate vaccine booster can be
administered.
References
- Dodds WJ. More bumps on the vaccine road. Adv Vet Med 41:715-732, 1999.
- Dodds WJ. Vaccination protocols for dogs predisposed to vaccine reactions. J Am An Hosp Assoc 38: 1-4, 2001.
- Hogenesch
H, Azcona-Olivera J, Scott-Moncreiff C, et al. Vaccine-induced
autoimmunity in the dog. Adv Vet Med 41: 733-744, 1999.
- Hustead
DR, Carpenter T, Sawyer DC, et al. Vaccination issues of concern to
practitioners. J Am Vet Med Assoc 214: 1000-1002, 1999.
- Kyle
AHM, Squires RA, Davies PR. Serologic status and response to
vaccination against canine distemper (CDV) and canine parvovirus (CPV)
of dogs vaccinated at different intervals. J Sm An Pract, June 2002.
- Lappin
MR, Andrews J, Simpson D, et al. Use of serologic tests to predict
resistance to feline herpesvirus 1, feline calicivirus, and feline
parvovirus infection in cats. J Am Vet Med Assoc 219: 38-42, 2002.
- McGaw
DL, Thompson M, Tate, D, et al. Serum distemper virus and parvovirus
antibody titers among dogs brought to a veterinary hospital for
revaccination. J Am Vet Med Assoc 213: 72-75, 1998.
- Paul MA. Credibility in the face of controversy. Am Anim Hosp Assoc Trends Magazine XIV(2):19-21, 1998.
- Schultz RD. Current and future canine and feline vaccination programs. Vet Med 93:233-254, 1998.
- Schultz
RD, Ford RB, Olsen J, Scott F. Titer testing and vaccination: a new
look at traditional practices. Vet Med, March 2002, pp 1-13.
- Scott
FW, Geissinger CM. Long-term immunity in cats vaccinated with an
inactivated trivalent vaccine. Am J Vet Res 60: 652-658, 1999.
- Scott-Moncrieff
JC, Azcona-Olivera J, Glickman NW, Glickman LT, HogenEsch H. Evaluation
of antithyroglobulin antibodies after routine vaccination in pet and
research dogs. J Am Vet Med Aassoc 221: 515-521, 2002.
- Smith CA. Are we vaccinating too much? J Am Vet Med Assoc 207:421-425, 1995.
- Tizard I, Ni Y. Use of serologic testing to assess immune status of companion animals. J Am Vet Med Assoc 213: 54-60, 1998.
- Twark
L, Dodds WJ. Clinical application of serum parvovirus and distemper
virus antibody titers for determining revaccination strategies in
healthy dogs. J Am Vet Med Assoc 217:1021-1024, 2000.
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