June 2023

In this VETgirl sponsored online veterinary continuing education blog, guest blogger Christopher Lee, DVM, MPH, DACVPM discusses the hesitancy pet owners may have when it comes to vaccines. Being that vaccines are listed in the top 10 public health achievements of the 20th Century, why is there so much percolating fear of vaccines, and what we can do about it as veterinary professionals?

Giving Dogs an EDGE in Vaccine Technology with Dr. Christopher Lee

By Christopher Lee, DVM, MPH, DACVPM

Hey, doc, why do my Chihuahua and my Great Dane dog both get the same dose of vaccines?

Well —

When I got my flu shot, it was only a half mL. Why does my dog get so much? C’mon doc, can’t you just give half to the little guy?

When we, as veterinary professionals, probe the “why” behind these pet owner questions, we often discover a percolating fear of vaccines. Vaccines rest first as the top ten of public health achievements of the 20th Century, yet many people remain hesitant to their use.


Image by No-longer-here from Pixabay

Since vaccines can generate a long-lasting amnestic response that can persist, in some cases, for decades or a lifetime, there is a dividing line for every individual – the time before receiving a vaccine and the time after. Thus, a list of unlikely and likely concerns has amassed.

Unlikely associations have changed over time and often reflect the current culture. Despite squelching the vast numbers of death and deformity from the smallpox virus, the anti-vaccination movement was born on the heels, or perhaps the “hoofs,” of vaccination. Two top concerns with using cowpox to prevent the deadly smallpox were “cowpox mange” and “cow mania.” Cowpox mange was the theorized risk of a vaccinated individual sprouting hoofs and horns, while cow mania was the potential of birthing half-human, half-cow children.

When considering known vaccine-induced diseases, few events linger in our mind, like the Cutter Incident of 1955. The day after the 1.8 million child vaccine trial proved successful, Salk’s polio vaccine was licensed. Within two weeks, five companies had distributed nearly five million doses. By design, these vaccines were inactivated, or killed, and thus, should have been free of any reversion to virulence.

Live polio virus contaminated the Cutter Laboratories vaccine product. In less than two weeks of vaccine institution, reports of polio infection arose. By the end of the incident, over 200,000 immunized people had been infected with the contaminated, live polio vaccine. Roughly half of these victims were children, and the resulting sequelae included death, paralysis, and muscle weakness. Within the canine veterinary channel, distemper and rabies reversion to virulence, older leptospirosis vaccine reaction rates, and lack of expected efficacy remain fixated within our fears of vaccine concerns.

Realizing the importance of regulation, the United States can be considered at the forefront of safeguarding the public. From the USDA and AVMA origins in the 1860s, to the generation of the FDA and associated laws in the early 1900s, drugs and vaccines have been continually held to increasingly higher standards. Specific to veterinary medicine, the Center for Veterinary Medicine (CVM) under the FDA was established in 1984 and the Center for Veterinary Biologics (CVB) under USDA was established in 1996.

As pet owners try to adjudge safety risk minimization options for themselves, volume is quick to mind. After all, human vaccines do vary by dose. Earlier vaccines, such as early polio vaccines and those distributed by Cutter, were often 1 mL in volume. Today, most people receive a 0.5 mL inactivated influenza vaccine, while some people, 65 and older, may receive a larger, 0.7 mL, dose. Many people are well acquainted with the 0.25 mL COVID-19 booster vaccine regimen. Other vaccines remain at 1 mL in volume.

Despite this range, the doses for each age range remain strict. For example, an 18 year, 11 month, and 29 day-old, regardless of weight or height, would still receive 0.5 mL of Hep A. Wait for that person to age a few days, and the mandatory dose would double.

The CDC houses the vaccine recommendations and guidelines of the Advisory Committee on Immunization Practices (ACIP). Their statement regarding reduced dose of vaccination is clear: “Any vaccination using less than the standard dose should not be counted.”

On the veterinary side, following the Virus-Serum-Toxin Act (VSTA), the Center for Veterinary Biologics (CVB) within USDA ensure that pure, safe, potent, and effective veterinary biologics are provided to animals within the United States. This includes research to identify the minimal immunizing dose required for each vaccine antigen or pathogen.

The AAHA Vaccine Guideline Website, in March 2023, addresses the concern of reducing the vaccine volume in small breed dogs: “The volume recommended by the manufacturer generally represents the minimum immunizing dose; therefore, the total volume of a vaccine dose should always be administered. Arbitrarily reducing the volume of a vaccine may result in an immune response that is less than protective. Furthermore, there is no evidence that lowering the dose/volume of a vaccine will prevent an adverse event.”

Targeting minimum potency levels helps with the concern of “my dog is so small” but doesn’t necessarily answer the “could this still be too much” question. Title 9 Code of Federal Regulations (9CFR) § 113.40 Dog Safety tests states that before any serial of a vaccine is released: “Each of two healthy dogs shall be administered 10 dog doses by the method recommended on the label and the dogs shall be observed each day for 14 days.”

We better understand the goalposts by combining the AAHA small breed question and the 9CFR testing. If some undefined amount of vaccine is lost during administration due to a wiggly pet, then being able to provide another complete dose represents clinical safety as defined by a 10x limited safety study on every lot released by a vaccine manufacturer. Thus, regardless of size, every dog should receive at least a complete dose for proper protection against disease.

As human and veterinary vaccines continue to innovate in safety and efficacy, new options continue to present themselves. In the last decade, many innovations for animals have arisen to make choosing a couple of examples challenging.

One example includes the RNA particle technology called SEQUIVITY®, which has been used to create customized prescription swine vaccines against selected strains of the influenza A virus. A vaccine tailored to a specific swine facility can be created for the producer in as little as eight to twelve weeks.

On the companion animal side, Merck Animal Health’s Nobivac EDGE® line produces the first-ever distemper, adenovirus type 2, parvovirus, and parainfluenza combination in a half-volume presentation. This half-volume line includes a four-serovar leptospirosis vaccine that is backed by data demonstrating the prevention of shedding and mortality. Finally, all these important antigens are available in a 0.5 mL EDGE® DAPPv+L4 option. As pet owners consistently embrace a less-is-more approach while rightfully expecting maximum protection, vaccines such as the Nobivac EDGE® line are a clear choice at the pinnacle of vaccine innovation.

1. Carapetis JR. The Cutter Incident: How America’s First Polio Vaccine Led to the Growing Vaccine Crisis. BMJ. 2006 Mar 25;332(7543):733. PMCID: PMC1410842.
2. CDC. (1999). Ten great public health achievements — United States, 1900-1999. Centers for Disease Control and Prevention. https://www.cdc.gov/mmwr/preview/mmwrhtml/00056796.htm#:~:text=Ten%20Great%20Public%20Health%20Achievements%20–%20United%20States%2C,babies%20%208%20Family%20planning%20%20More%20items
3. Commissioner, O. of the. (n.d.). Frances O. Kelsey. U.S. Food and Drug Administration. Retrieved April 18, 2023, from https://www.fda.gov/about-fda/fda-history-exhibits/frances-oldham-kelsey-medical-reviewer-famous-averting-public-health-tragedy
4. Director, M. D. P. D., Director, A. M. D. P. D., & Director, M. D. P. D. (2023, January 23). Vaccines can help make a better life possible for everyone. IFPMA. Retrieved April 18, 2023, from https://ifpma.org/insights/vaccines-can-help-make-a-better-life-possible-for-everyone/
5. Fitzpatrick M. The Anti-Vaccination Movement in England, 1853-1907. J R Soc Med. 2005 Aug;98(8):384–5. PMCID: PMC1181850.
6. McHugh, J. (2021, November 10). The world’s first anti-vaccination movement spread fears of half-cow babies. The Washington Post. Retrieved April 18, 2023, from https://www.washingtonpost.com/history/2021/11/14/smallpox-anti-vaccine-england-jenner/

This VETgirl online veterinary continuing education blog is sponsored by Merck Animal Health, makers of Nobivac® vaccines. Our dogs are part of our families. We want to make sure they stay healthy. Nobivac EDGE® vaccines include unique, effective, 0.5-mL solutions that deliver full-sized protection in half the volume. Ideal for smaller dogs, but equally effective in large dogs, too. Put comfort into practice with Nobivac® vaccines.

This VETgirl online veterinary continuing education blog is sponsored by Merck Animal Health. Please note the opinions in this blog are the expressed opinion of the author(s), and not directly endorsed by VETgirl.

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