Canine Vaccination Guidelines: Key Points for Veterinary Practice

Richard B. Ford, DVM, MS, Diplomate ACVIM & ACVPM(Hon)

In 2011, the Canine Vaccination Task Force, sponsored by the American Animal Hospital Association (AAHA), revised vaccination guidelines for dogs.¹

These canine vaccination guidelines have an immediate impact in private practice, with emphasis on 3 key areas:

1. Developing vaccination protocols
2. Vaccine adverse reactions
3. Fundamental legal concerns surrounding vaccine administration.

Highlighted throughout this article are key points that represent some of the most important and new recommendations relative to developing and implementing a vaccination protocol.

DETERMINING PROTOCOLS

Within the U.S. and Canada, veterinarians who administer vaccines must select from among a wide variety of proprietary (trade name) products, each of which is backed by technical data defining safety and efficacy; then promoted through a robust marketing message.

Interestingly, the ultimate decision regarding selection and use of vaccines is frequently reduced to a reasonable assessment of exposure risk and determination of product cost. It is not surprising, therefore, that considerable diversity exists among companion animal practices regarding vaccine administration.
To facilitate implementation of rational vaccination protocols in individual practices, a task force comprised of practicing veterinarians, specialists, academicians, and legal experts, with input from each of the major vaccine manufacturers, created revised canine vaccination guidelines in 2011.¹ Whenever possible, the recommendations are based on the most current scientific studies; recommendations not backed by published studies are based on unpublished studies, sound immunologic principles, or expert opinion.

CLASSIFYING VACCINES

The vaccination guidelines separate vaccines into 2 groups:

• Core: Vaccines that offer protection against highly contagious, life-threatening infections or infections that pose a significant threat to human health (eg, rabies).
• Noncore: Vaccines that offer protection against less serious health threats to dogs or threats that pose a regional health risk.

Table 1 summarizes core and noncore canine vaccines as represented in the vaccination guidelines. The oral Bordetella bronchiseptica vaccine was not available at the time the guidelines were published but is categorized by the author as a noncore vaccine based on available information.²

Remember that the 2011 AAHA Canine Vaccination Guidelines are recommendations; they are not requirements. It is ultimately the decision of the individual veterinarian or practice to establish which vaccines in a protocol are designated core or noncore.

CORE VACCINES

Vaccines designated as core should be administered to all dogs. The AAHA Canine Vaccination Task Force defines the following vaccines as core:

• Distemper virus (CDV)
• Parvovirus (CPV)
• Adenovirus-2 (CAV-2)
• Rabies (RV).

Initial Vaccination of Young Dogs

Vaccination Other Than Rabies
Current recommendations for initial vaccination of young dogs stipulate that, with the exception of rabies, 3 doses of a combination core vaccine be administered between 6 and 16 weeks of age. In practice, a single combination dose is typically recommended for administration at 2, 3, and 4 months of age (Table 2).

Dosing Interval. Today, most manufacturers offer combination core vaccines with the recommendation to administer 2 doses by 12 weeks of age.³ The guidelines, however, emphasize the importance of administering a third dose (or the final dose) between 14 and 16 weeks of age. This recommendation is based on observations that, in some dogs, the level of maternally derived antibody may be sufficiently high to interfere with vaccines administered at 12 weeks of age, particularly CPV.

Recombinant Technology. The recombinant canine distemper virus (rCDV) vaccine can be used interchangeably with the modified-live canine distemper virus (MLV CDV) vaccine in practice. Characteristics unique to recombinant technology have been addressed in the guidelines:

• The rCDV vaccine is incapable of replicating in dogs and, therefore, reversion to a virulent CDV is not possible.¹
• In addition, the rCDV vaccine uniquely immunizes young dogs as much as 2 weeks earlier than conventional MLV CDV vaccines.4-7 For this reason, rCDV vaccination may have significant advantages over MLV vaccination in young dogs at risk for exposure to CDV.

Rabies Vaccination
The first dose of rabies vaccine should be administered in accordance with state or local statute.

• Within the U.S., rabies vaccination should not occur in any dog (or cat) less than 3 months of age.³
• Initial vaccination is generally not regarded to confer immediate immunity against rabies. In most states, a dog is not legally immunized against rabies until 28 days following initial vaccination.⁸
• Rabies vaccination requirements for dogs vary significantly among states: In some states, rabies vaccination for dogs is not specifically required. Within these states, however, a local (city or county) rabies vaccination ordinance may be in effect.
• Where no state or local ordinance exists, veterinarians are encouraged to recommend rabies vaccination in accordance with guidelines from the National Association of State Public Health Veterinarians;8 a suggested protocol is outlined in Table 2.

Revaccination Intervals in Adult Dogs

Revaccination Other Than Rabies
A single dose of combined core vaccines (CDV/CPV/CAV-2) should be administered within 1 year of initial core vaccination, regardless of the product used.¹ This recommendation ensures that a patient receives core vaccines at an age when maximum (protective) response to the antigens can be expected.

With the exception of rabies vaccine, adult dogs should be revaccinated with a single dose of core vaccines (CDV/CPV/CAV-2) every 3 years or longer, regardless of the product used.¹ This recommendation highlights 2 principal facts:

1. The duration of protective immunity conferred by administration of core vaccines in adult dogs extends at least 5 years, and probably longer.^2,9-14
2. With the exception of rabies vaccination, veterinarians have considerable latitude in recommending vaccination booster intervals.¹

While vaccine manufacturers may recommend administration of “annual boosters” for adult dogs, the recommendation does not constitute a legal mandate to do so. Most manufacturers include minimum duration of immunity data on product package inserts, which meets or exceeds 3 years.³

Rabies Revaccination
Where rabies revaccination is required for dogs, a single dose is typically required within 1 year following the initial dose, regardless of the dog’s age when the initial dose was administered.⁸ Generally, a dog that is not revaccinated within 1 year following the initial dose is legally not immunized.

In most states, the second dose of rabies vaccine in the initial 2-dose series may be labeled as a 1- or 3-year rabies vaccine; the duration of immunity following administration is contingent on this product labeling. In some states, however, local statutes may impose requirements that are stricter than state requirements (eg, annual rabies vaccination). Veterinarians should be familiar with local rabies immunization requirements for dogs.

NONCORE VACCINES

Vaccines designated as noncore, or optional, are those that a veterinarian may recommend for individual patients in the event there is reasonable risk for exposure to the infectious virus or bacteria. Unfortunately, comprehensive guidance on which locations pose the highest risk for exposure to specific pathogens is not available. Therefore, the decision whether to administer a particular noncore vaccine is left to the veterinarian. Such decisions should be based on known geographical risk for exposure to a pathogen combined with knowledge of lifestyle factors unique to the individual dog. Table 1 lists noncore vaccines for dogs.

Initial Vaccination

With the exception of vaccines licensed for intranasal administration to dogs (eg, those containing Bordetella bronchiseptica avirulent live bacteria) and the oral B bronchiseptica vaccine, all noncore vaccines require at least 2 initial doses, administered 2 to 4 weeks apart, to immunize.

A single dose of a parenterally administered noncore vaccine is not expected to induce a protective immune response. If a dog is presented for the second dose 6 weeks or longer after the initial dose, it is generally recommended to repeat the initial series by administering 2 additional doses, 2 to 4 weeks apart.

Key Point: Regardless of a dog’s age or the vaccines used, the minimum administration interval for noncore vaccines is 2 weeks.

Adult Revaccination

Following completion of the initial 2-dose series of a noncore vaccine, and assuming a reasonable risk for exposure is sustained, annual revaccination with the appropriate noncore vaccine is recommended. There are no recommendations for intervals extending beyond 1 year for noncore vaccines.

Key Point: The revaccination interval for noncore vaccines is every 12 months as long as a reasonable risk for infection exists; there are no extended interval recommendations.

Not Recommended

The AAHA Canine Vaccination Task Force recommends NOT using either the killed or MLV canine coronavirus (CCoV) vaccine. This designation is not based on safety issues pertaining to any licensed product; instead, it is based on the facts that (1) dogs derive limited to no protective immunity from the vaccine and (2) CCoV does not cause significant disease. However, CCoV vaccines are licensed by the USDA and may be administered at the discretion of the individual veterinarian.

VACCINE ADVERSE REACTIONS

A vaccine adverse reaction (or adverse event) refers to any undesirable, or unintended, effect associated with the administration of vaccines, including failure to immunize. Unfortunately, vaccine adverse reactions in veterinary medicine are significantly underreported, making it impossible to determine actual adverse event rates. However, considering the number of vaccines administered yearly, it is generally agreed that adverse reactions are relatively uncommon in dogs.

Despite lack of data, certain risk factors have been identified. The guidelines include recommendations on:

• Mitigating risk
• Treatment of acute-onset reactions
• Revaccination of patient with known or suspected vaccine adverse event history.

Adverse Reactions

Because vaccines are biologically active products and potent immunostimulants, minor reactions can be expected in any dog. Common adverse reactions reported to manufacturers include:

• Postvaccinal lethargy
• Pain (discomfort)
• Inappetance
• Lumps at the injection site.

Owners should be advised to anticipate minor reactions such as these for 1 to 2 days after vaccination.
Advise clients to contact the practice if the following signs develop: vomiting, diarrhea, seizures, difficulty breathing or rapid respirations, facial swelling, or collapse. If a patient’s condition worsens or shows no improvement within 48 hours, follow-up examination is recommended.

Revaccination & At-Risk Patients

In general, revaccination of patients with a known or suspected history of a serious adverse vaccine reaction is not recommended.

In addition, patients with prior diagnosis of immune-mediated disorders (eg, immune-mediated hemolytic anemia, thrombocytopenia) should probably not receive additional vaccines due to the belief that vaccine administration may reactivate the disorders; however, this concern has not been validated in scientific studies.

In these patients, determining the antibody titer of the core vaccines (especially CDV and CPV) will provide reliable information on the individual’s immune status. Several states give veterinarians the authority to exempt rabies vaccination in patients that have a diagnosed illness or a prior history of a vaccine adverse event. However, if a patient is exempted from rabies vaccination, it is important to inform the client that, if the dog bites someone, it will be treated as a nonvaccinated dog.

Small Breed Dogs

For the first time, the guidelines have addressed administering vaccines to small breed dogs (< 20 pounds at the estimated adult weight). Published studies and practitioner experience support the fact that small breed dogs may have increased risk of experiencing vaccine adverse reactions, especially when multiple vaccines are administered at the same time.^15-18

It is now recommended that, in small breed dogs of all ages, noncore vaccines be administered 2 or more weeks after core vaccine administration.¹ While this recommendation requires additional appointments, reports from veterinarians indicate that owner compliance is high, particularly when owners are told that the reason for additional visits is patient safety.

Key Point: To mitigate the risk of adverse reactions in small breed dogs, administer noncore vaccines at least 2 weeks or longer after administration of core vaccines.

VACCINATION LIABILITY

Veterinarians are concerned about potential liability associated with following recommendations other than those from the manufacturer. For example, is a veterinarian legally liable if a dog, not vaccinated annually in accordance with manufacturer label recommendations, develops an infection preventable by vaccine (eg, CDV) after revaccination at a 3-year interval?

Legal Considerations

The reader is encouraged to review the Legal Considerations section of the 2011 AAHA Canine Vaccination Guidelines.¹

• Critical information concerning professional discretion in use of vaccines, medical negligence related to vaccine administration, consent versus informed consent, and medical record documentation are discussed in detail.
• Although the guidelines may differ from statements on product labels, veterinarians practicing in the U.S. and Canada do have considerable discretion in the selection and use of vaccines; rabies vaccination is an obvious exception.
• Adopting recommendations outlined in the guidelines is consistent with scientific principles of immunization and good medical practice.
• As highlighted in the guidelines, practitioners must determine the vaccination protocols that best suit their practices and level of risk tolerance.

While all USDA-licensed vaccines, regardless of minimum or maximum duration of immunity, have a package insert that says, “annual revaccination recommended,” this statement does not imply that annual revaccination is necessary to maintain immunity.

Key Point: With the exception of rabies vaccine, veterinarians have considerable ability to use biologics (vaccines) in a discretionary manner.

Client Discussions

Discussing potential risks associated with vaccine administration with clients is not inherently different than discussing the risks of a medical procedure or treatment.

• During an initial vaccine appointment, a thorough discussion of potential adverse reactions should be presented and documented in the medical record. On subsequent vaccination visits, a less extensive discussion is appropriate.
• If a veterinarian believes significant health risks may be associated with vaccine administration to an individual patient and elects to recommend against vaccination, the reasons for the recommendation should be discussed with the client and clearly noted in the medical record.¹
• In some states/municipalities, veterinarians may not have the option to recommend against rabies vaccination, regardless of the patient’s health status or perceived risk for an adverse reaction.

COMING UP

In the upcoming November/December issue of Today’s Veterinary Practice, the 2012 AAFP Feline Vaccination Guidelines will be reviewed. The January/February 2013 issue will present the first article in our new vaccination column, which will address vaccination concerns raised by practicing veterinarians.

CAV-2 = adenovirus-2; CDV = distemper virus; CCoV = coronavirus; CPV = parvovirus;
MLV = modified-live virus; MLV CDV = modified-live canine distemper virus; rCDV = recombinant canine distemper virus; RV = rabies

References

1. Welborn LV, DeVries JG, Ford RB, et al. 2011 AAHA Canine Vaccination Guidelines. Available at aahanet.org; accessed July 6, 2012.
2. Hess TJ, Parker DS, Hassal AJ, Chaing Y. Evaluation of efficacy of oral administration of Bordetella bronchiseptica intranasal vaccine when used to protect puppies from tracheobronchitis due to B bronchiseptica infection. Intern J Appl Res Vet Med 2009; 9(3):300-305.
3. Manufacturers’ product labels.
4. Pardo MC, Bauman JE, Mackowiak M. Protection of dogs against canine distemper by vaccination with a canarypox virus recombinant expressing canine distemper virus fusion and hemagglutinin glycoproteins. Am J Vet Res 1997; 58(8):833-836.
5. Hageny TL, Haase CJ, Larson LJ, et al. A comparison between recombinant, naked DNA and modified live canine distemper virus (CDV) vaccines. Conference of Workers in Animal Disease 2004; poster presentation abstract 65.
6. Larson L, Schultz RD. Effect of vaccination with rCDV vaccine immediately before exposure under shelter-like conditions. Vet Ther 2006; 7(2):113-118.
7. Pardo MC, Tanner P, Bauman J, et al. Immunization of puppies in the presence of maternally derived antibodies against canine distemper virus. J Comp Pathol 2007; 137:S72-S75.
8. Compendium of animal rabies prevention and control, 2011. National Association of State Public Health Veterinarians, Inc. MMWR 2011; 60(6):1-20.
9. Schultz RD, Thiel B, Mukhtar E, et al. Age and long-term protective immunity in dogs and cats. J Comp Pathol 2010; 142:S102-S108.
10. Larson LJ, Sawchuck S, Schultz RD. Duration of vaccinal immunity in a population of clinic dogs. Conference of Research Workers in Animal Disease 2002; abstract 75P.
11. Schultz RD. Duration of immunity for canine and feline vaccines: A review. Vet Microbiol 2006; 117(1):75-79.
12. Gill M, Srinivas J, Morozov I, et al. Three-year duration of immunity for canine distemper, adenovirus, and parvovirus after vaccination with a multivalent canine vaccine. J Appl Res Vet Med 2004; 2(4):227-234.
13. Larson LJ, Schultz RD. Three-year duration of immunity in dogs vaccinated with a canarypox-vectored recombinant canine distemper virus vaccine. Vet Ther 2007; 8(2):101-106.
14. Larson LJ, Schultz RD. Three-year serologic immunity against canine parvovirus type 2 and canine adenovirus type 2 in dogs vaccinated with a canine combination vaccine. Vet Ther 2007; 8(4):305-310.
15. Roth JA. Mechanistic bases for adverse vaccine reactions and vaccine failures. Adv Vet Med 1999; 41:681-700.
16. Frana TS, Elsken LA, Karli SA. Summary of adverse event reports for veterinary biologic products received by the USDA from 1999 through 2005. JAVMA 2006; 229(7):1100-1102.
17. Meyer EK. Vaccine-associated adverse events. Vet Clin N Am Small Anim Prac 2001; 31:493-514.
18. Moore GE, Guptill LF, Ward MP, et al. Adverse events diagnosed within three days of vaccine administration in dogs. JAVMA 2005; 227(7):1102-1108.

Richard B. Ford, DVM, MS, Diplomate ACVIM & ACVPM(Hon), is Emeritus Professor of Medicine at North Carolina State University’s College of Veterinary Medicine. He is a retired Brigadier General from the USAF Reserve, where he was assigned to the Office of the Surgeon General at the Pentagon. Dr. Ford is also a past president of the NAVC Conference and continues his role as a member of the scientific program committee. His clinical interests are in the field of companion animal infectious disease; he is a prolific author and serves on both the AAHA Canine Vaccination Task Force and AAFP Feline Vaccination Advisory Panel. Dr. Ford received his DVM from Ohio State University and completed an internal medicine residency at Michigan State University. He held a previous faculty position at Purdue University.