Local forum raises question on necessity of annual
vet vaccines
by Dr. David L. (“Woody”) Woodland
(as published in the Summit Daily News of February 9, 2015)
Earlier this month, Keystone Symposia on Molecular and Cellular Biology held a free public
community forum on “The Viral Threat in the Age of Ebola.” The event, which took place at the
Colorado Mountain College auditorium in Breckenridge, featured two leading experts in viral
immunity and was well attended by the local community. As is usually the case, there were
many excellent questions from the audience. But one question stumped the speakers and me.
The questioner asked whether the immune systems of bovine and canine species are different
from those of humans, necessitating repeat immunizations each year. He pointed out that
animal vaccines usually have to be given every year, which is quite different than with most
human vaccines.
Embarrassed at not being able to definitively answer this question, I reached out to a couple of
experts in the field, Dr. William Golde from the Plum Island Animal Disease Center in New York
and Dr. John Barlow from the University of Vermont. Both of these scientists gave very similar
answers. In principle, they argued that we have more detailed knowledge about human vaccine
efficacy because manufacturers are willing to spend a lot more on development; human
vaccines can be sold at a price that recoups the considerable investment in testing and
production. In contrast, the price point for companion pet and agricultural vaccines is lower,
resulting in less testing. Livestock vaccines can’t be sold for more than a dollar a dose and
vaccines for fowl for just pennies a dose. As a result, there are only limited incentives to do the
costly trials necessary to evaluate extended protection in companion and food animal medicine.
Additionally, the approval process itself does not require demonstration of long-term efficacy.
Thus, given the lack of any other information, the label indication on the finally approved vaccine
will indicate the need for re-vaccination. The rabies vaccine is an exception to the rule of annual
boosters; formulations may have labels for boosters at two and three years because the
challenge studies have been done to determine durability.
The two scientists also pointed out a second reason some animal vaccines may need to be
given on a regular basis. Many food animals are maintained in herds subject to rapid population
turnover. A good example of this is the dairy industry where 20-30% of the herd might be
replaced in a single year. In these cases, vaccinating the whole herd every year is simply easier
than identifying individual animals needing vaccination. In contrast, beef herds have lower levels
of turnover as the mothers remain in the herd producing new calves each year (only the calves
are sold out of the herd). Repeated vaccination may not be necessary in these cases. The same
may be true for the poultry, swine and aquaculture industries where the animals are grouped in
age cohorts and managed as "all-in and all-out" populations (i.e., the facilities depopulated
when the group moves to another facility or to slaughter), and then the facilities are sanitized
and repopulated with a new cohort.
While regulatory controls of animal vaccines are less stringent than for human vaccines, there
are nevertheless numerous controls over their production. For animal health companies to
manufacture and sell veterinary vaccines, they must have an establishment license and a
product license, both of which are granted by the Center for Veterinary Biologics, a branch of
the United States Department of Agriculture. Key criteria required for approval are safety,
efficacy and potency. These controls over animal vaccines may become more critical as we
enter an era in which prophylactic use of antibiotics in food animals is prohibited.
There is no question that veterinary vaccines have greatly improved the health and welfare of
companion animals and increased the production of livestock. I would like to thank the
questioner at our event for encouraging us to think about the value and economics of veterinary
vaccines, as well as the two animal vaccine experts who weighed in on this important issue.
David L. “Woody” Woodland, Ph.D. is the Chief Scientific Officer of Silverthorne-based Keystone
Symposia on Molecular and Cellular Biology, a nonprofit dedicated to accelerating life science discovery
by convening internationally renowned research conferences in Summit County and worldwide. Woody
can be reached at 970-262-1230 ext. 131 or woody@keystonesymposia.org.
For more (Petri) Dish columns, visit www.keystonesymposia.org.