The Giardia vaccine is not recommended by the AVMA, Cornell University, Tufts University, or UCDavis University (the 3 main schools involved in Vaccine research and publish vaccine guidelines on a regular basis). It is definately zoonotic, and the fact that a vaccine isn't offered to humans (even though it public health reportable, and wide-spread) is an indicator that the vaccine isn't ready to use on my dogs. My personal belief is that as vaccines are developed for zoonotic diseases, they are tested wide-scale in the veterinary market before they are approved by the FDA, great huh?
Here's the abstract from a recent JAVMA article concerning Giardia Vaccine:
J Am Vet Med Assoc. 2003 Jun 1;222(11):1548-51. Related Articles, Links
Efficacy of Giardia vaccination in the treatment of giardiasis in cats.
Stein JE, Radecki SV, Lappin MR.
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
OBJECTIVE: To assess efficacy of Giardia vaccination as a treatment for giardiasis in experimentally infected cats. DESIGN: Original study. ANIMALS: 16 young-adult cats. PROCEDURE: Cats were experimentally infected by orogastric administration of Giardia cysts. On weeks 4, 6, and 10, cats in the treatment group (n = 8) were given Giardia vaccine SC. For the first 28 weeks after infection, 3 fecal samples from each cat were examined weekly for Giardia cysts, and cyst numbers were counted. Fecal consistency was scored daily for the duration of the study. Results from vaccinated and unvaccinated cats were compared by logistic regression. RESULTS: All cats became infected and were shedding Giardia cysts by the end of week 2. Throughout the study, diarrhea was rare and was mild and transient when it did occur. By week 28, 5 of 8 vaccinated cats and 7 of 8 control cats had patent Giardia infections. Magnitude of infection, based on number of fecal samples with cysts and number of cysts per sample, decreased progressively in both groups over time. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of 3 doses of a Giardia vaccine did not completely eliminate the organism from experimentally infected cats in the study period. Since clinical signs were minimal in both groups of cats, it could not be determined whether vaccination lessened severity of clinical disease. Results may have been negatively influenced by the large inoculation dose. Whether Giardia vaccination is an effective treatment for giardiasis in naturally infected cats remains to be determined.
Along with Coronavirus vaccine, Giardia Vaccine is on Cornell's list of "NOT RECOMMENDED VACCINES" for dogs for the following reasons:
Giardia Not recommended
1. Efficacy of Vaccine unsubstantiated by independent studies.
2. IgA mucosal antibodies? Immunity against a complex organism?
3. Natural infection does not provide immunity.
Basically meaning, the vaccine's usefulness lacks testing, the immunity against the giardia organism depends on the vaccine antibodies' ability to recognize a particular strain of giardia parasite, and lastly, since giardia is not a viral organism, the body does not build up natural antibodies to it upon infection (like your chi would with distemper or parvo vaccine). All the vaccine does is circulate engineered chemicals to disrupt the life cycle of giardia (uneffectively).
Will there be a time when Giardia vaccine will be useful? Maybe, but not right now.
-Nate