Dispelling Misperceptions of Vaccines in Veterinary Medicine

Vaccine hesitancy (ie, reluctance or refusal to vaccinate despite the availability of vaccines) has been named one of the top 10 threats to global health by the World Health Organization (WHO).¹ Increasing evidence demonstrates that the human antivaccine movement impacts pet owners and that >50% of dog owners report some degree of vaccine hesitancy.^2,3

In human medicine, self-advocacy, in which patients develop a knowledge base and assert themselves when communicating with health care providers, is important.⁴Pet owners attempting this approach may seek information from the internet, friends, family members, breeders, pet store employees, and groomers. Information and misinformation obtained from these sources can be frustrating to address, but most vaccine-hesitant owners are simply attempting to advocate for their pet’s well-being and are not truly opposed to vaccines.

The primary concerns prompting hesitancy about pet vaccines (aside from cost) are that vaccines are unnecessary and/or unsafe.^2,5 Owners who decline recommended vaccines should be asked about their reasoning. Recognizing these concerns can build trust, even if the owner’s decision not to vaccinate does not change.

Myth: Vaccines Are Unnecessary

Owners who decline vaccines often believe their pet has a negligible risk for contracting disease on the basis that vaccine-preventable diseases are uncommon or that risk is nonexistent for pets housed indoors or otherwise not in known contact with other animals.^2,5 Addressing these conceptions pre-emptively can be helpful. For example, instead of saying “Daisy is due for xyz vaccination,” a team member can indicate awareness of the patient’s lower-risk lifestyle by saying “As an indoor pet, we recommend Daisy be vaccinated against xyz.” Explanation of the disease being vaccinated against and risk factors for exposure can be given to more hesitant owners or those seeking additional information. For example, regular annual FeLV revaccination is not typically recommended for adult indoor-only cats because direct animal contact is needed for disease spread. Conversely, canine parvovirus and feline panleukopenia are endemic viruses that can be spread via fomites (eg, owner’s shoes), so even indoor-only animals are at risk.⁶

Rabies

Although ≈59,000 human rabies deaths occur worldwide each year,⁷ a frequent misconception is that rabies has been effectively eradicated in the United States. Owners should be educated on rabies prevalence in their region. For example, from 2017 to 2021, an average of 47 rabies-positive cats were identified each year in Pennsylvania. During the same time period, an average of 1,500 rabies-positive bats were identified annually in the United States, including cases in all 48 continental states.^8-12 Bats can enter a home without the homeowner being aware and thus present a risk for indoor pets. In a study of 41 humans infected with confirmed bat-variant rabies virus in the United States, only 7 had a known bat bite and 17 had no known history of bat exposure.¹³ Pets living indoors and pets in less endemic regions may have decreased risk for rabies exposure, but the risk is not zero.

Vaccination Frequency

Vaccination frequency, which is related to duration of immunity, is a valid concern for some owners. Certain vaccines, particularly those that stimulate robust sterilizing humoral immune responses (eg, canine parvovirus, adenovirus, and distemper virus; feline panleukopenia virus), may provide protection for significantly longer than the labeled 3 years.^14,15 Antibody titers may be considered to assess persistence of immunity prior to administration of these vaccines, although patients with low titer results may still be protected via anamnestic and cellular immune responses. Extended durations of immunity are less likely for nonsterilizing viral (eg, feline herpesvirus, calicivirus^15,16) and bacterial (eg, leptospirosis, Lyme disease, Bordetella bronchiseptica) vaccines. Vaccinations should not be discontinued in healthy, older patients based on age, as immune function is known to diminish in aging patients; the importance of vaccines may be increased for elderly patients.^17-19

Myth: Vaccines Are Unsafe

Owner concerns about vaccine safety are legitimate and deserve recognition, as adverse effects (eg, anaphylaxis, vaccine-associated injection-site sarcomas in cats) can be life-threatening; however, these situations are rare, particularly compared with risks of vaccine-preventable diseases.

Data indicate that 1 in 515 dog vaccine visits and 1 in 492 cat vaccines have resulted in an adverse reaction significant enough to be documented in the medical record.^20,21 Most of these cases are not life-threatening. Reported rates of death during the postvaccination period are ≈1/1,000,000 to 1/100,000 for dogs and ≈1/100,000 to 1/10,000 for cats.^13,17,21-25

Mild vaccine-associated adverse effects, particularly those resulting from physiologic immune responses, are typically less tolerated in veterinary medicine compared with human medicine. For example, a human patient receiving an influenza vaccine may be advised that arm pain is normal. In contrast, a small animal patient with signs of injection site pain may be experiencing a normal physiologic response but should be evaluated and treated (eg, with an NSAID), if only for quality-of-life purposes. Expectations should be communicated clearly to owners. For example, “It is normal for Daisy to be tired after receiving her vaccines. It is not normal for Daisy to feel sick or painful, and it would definitely not be normal if she were to break into hives, get puffy lips, or experience vomiting.”

Although longer-term impacts of vaccines (eg, vaccinosis) are implicated by online sources and may be of concern to owners,² there is little scientific evidence to support existence of such entities.

Conclusion

Veterinary team members should clearly communicate vaccine recommendations to owners, including using supportive statements about the reasons for recommendations.^26,27 The tone should avoid privileging positivism, in which it is assumed that the clinician has all the knowledge and power and the owner has no choice but acceptance. For example, the introductory statement “I strongly recommend vaccinating Daisy against rabies today,” may be better received than “Today, we are giving Daisy a rabies vaccine.” This approach is also more likely to result in compliance than “What do you think about vaccinating Daisy for rabies today?” For owners who express vaccine hesitancy, the initial recommendation should be followed by invitational communication, in which owners are invited to express their thoughts and concerns through open dialogue.²⁸

Veterinary teams must keep in mind that the final decision on whether to vaccinate a patient belongs to the owner. The role of the veterinary team is not to force vaccination but instead to educate and support owners in making the best possible decisions. Whether or not an owner’s concern is scientifically founded, failure to respect their views is likely to result in owner dissatisfaction, lower compliance, and worsened outcomes for the pet. Acknowledging the owner’s advocacy helps build trust.