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Vaccines Made Easy

Vaccines Made Easy

By Kathryn Primm, DVM

Why Do We Recommend Vaccination?

Infectious disease has existed as long as history has been documented. In 1796, a country physician named Edward Jenner administered the first documented inoculation. Smallpox was a devastating epidemic, killing millions of people during the 20th century. Dr. Jenner had noticed that milk maids, who had been exposed to cowpox (as evidenced by pustules on the hands and arms), did not become ill from the smallpox outbreaks. Cowpox did not cause significant illness and death in humans, so Jenner famously inoculated a boy with pus from a Cowpox lesion on a milk maid’s hand and then was able to demonstrate the boy’s resistance to infection from future exposure to Smallpox. (1,2) The Smallpox vaccine saved millions of lives that would have been lost to Smallpox epidemics. For centuries, vaccination has been saving lives and today’s vaccines are significantly improved over a pus sample!

How Do Vaccines Do Their Job?

Vaccines work by engaging the immune system in a “mock battle” so that it is armed and ready to react swiftly and effectively when exposure to the actual pathogen occurs. Immune systems are amazing in the way they can respond to threats and then be able to “remember” markers that flag the infectious agent. The next time the threat attacks, the immune system quickly recognizes the marker and calls up the appropriate cells to fight.

In the case of the Cowpox and Smallpox exposure, the viruses are so similar that an immune reaction to Cowpox would trigger resistance to Smallpox as well, so when the boy was exposed to Smallpox after the Cowpox, his immune system engaged in a rapid battle to eliminate it.

Vaccines take advantage of this extraordinary ability. They are able to teach the immune system how to recognize a specific threat without actually being at risk. They accomplish this feat through an inactivated threat (killed vaccine) or by utilizing the actual pathogen, modified to be harmless, just like the inoculation of the boy with the harmless Cowpox primed his immune system to be ready for attack from Smallpox. There are different types of vaccines, but the goal of all of them is to reduce infection and subsequent death from the disease.

How Do We Decide Which Vaccines are Appropriate?

Many diseases with a high mortality (lots of individuals die) and/or high morbidity (high numbers become ill) are the ones for which vaccines are developed. Most vaccine protocols are based on the individual pet’s lifestyle and risk factors.

Gone are the days when vaccination is a “one size fits all” concept. Each pet should be treated as an individual, taking into account his/her history, age, species, breed, lifestyle, environment, and disease risk factors. Be sure the appropriate questions are being asked when deciding the vaccine choices and only the necessary ones are recommended and administered according to local laws.

Why Do We Repeat (Booster) Vaccines?

The immune system is able to remember threats for a time. We don’t really know how long that time is for your individual pet and it is better to truly have current protection than to think that a pet is protected when he is not. Young animals always require multiple boosters of certain vaccines because some of the immunity that they get from their mothers can interfere with the effectiveness of their own immune recognition. We need to make certain that the vaccine is present when the maternal interference wanes and it is somewhat variable in each animal.

Are Vaccines Safe?

There has been an odd push on the Internet and social media to smear vaccinations and blame them for a variety of health issues, ranging from cancer to autism. Educated and informed medical sources have refuted many of these claims. Be aware that, by and large, vaccination is a very good idea and has saved countless animal and human lives.

There are rare cases of allergic reactions to vaccines and these should be handled on an individual basis. That is not to say that random vaccines should be given regardless of risk because even though the risk of complications is small, if the chance of disease is smaller, one must find the balance. Those that speak out against vaccination may have forgotten that their ancestors might not have survived at all without them.

Why Do I Need to Know
About Vaccines?

As a pet business professional, you are viewed by the public as an influencer in the area of animal health. You want to be sure that you stay aware of all the current recommendations so that you can confidently answer questions and concerns. As the animal’s advocate, you may be the only source of credible information to combat the onslaught of bad advice.

In most cases, the risk of disease far outweighs the risk of significant side effects and pets should be vaccinated with vaccines deemed necessary by the pet’s veterinarian. Some vaccines protect pets from diseases that are zoonotic (infectious to humans) and because of human health risk, at–risk pets must be identified and vaccinated properly.


  1. R.A. Meckel, “Levels and Trends of Death and Disease in Childhood, 1620 to the Present,” in Children and Youth in Sickness and Health: A Handbook and Guide, ed. J. Golden, R.A. Meckel, and H.M. Prescott (Westport, Conn.: Greenwood Press, 2004), 3–24
  2. E. Jenner, Inquiry into the Causes and Effects of the Variolae Vaccine (London: Sampson Low, 1798), 45.

Kathryn Primm, DVM is the owner and founder of Applebrook Animal Hospital in Ooltewah, Tennessee.  She has written and contributed content to many outlets, including magazines like Woman’s Day, Prevention and Health as well as Veterinary Economics, dvm360, Firstline, Vetted and Her regular “Ask A Vet” column is featured on and