Vaccination of dogs and cats

Policy

Every dog and cat should be appropriately immunised, and each individual animal should be vaccinated as frequently as considered necessary by their veterinarian to provide protection.

The vaccination protocol to be followed and the vaccines to be used should be determined within a veterinarian–client–patient relationship. The decision should be determined by factors such as the individual animal’s health status, the animal’s age and likely effects of maternally derived antibodies (MDA), the particular disease and environmental risks to the animal, and the duration of immunity (DOI) of available vaccines.

Background

Vaccination is one of the most common veterinary procedures undertaken in small animal practice. Over the past 5 decades, vaccines have demonstrated proven life-saving benefits with minimal associated risks. Vaccination programs have not only played an important role in preventing infectious diseases, they have helped foster early detection and treatment of other diseases through promoting regular clinical examinations during the life of the animal.¹

Vaccination recommendations in the past were considered a simple part of animal care, but they are now considered a complex and controversial issue.¹ While vaccination in general is considered very safe, vaccine associated adverse events are possible, and therefore when considering an appropriate protocol for a patient, veterinarians should aim to reduce the vaccine load on individual animals² provided this does not increase the risk of disease.

Adverse vaccine experiences are defined as any side effect, unintended consequence or lack of protection associated with the administration of a vaccine product.³ This includes any injury, toxicity or hypersensitivity reaction associated with the vaccination. The majority of adverse reactions are transient and self-limiting. The severest forms of adverse reactions, such as injection site sarcoma development in cats, are very rare.

Serological (or titre) testing is a method of assessing immunity prior to vaccination and it has for some time been used in published studies as a method of determining DOI.^4,5,6,7,8 Serological testing cannot determine true protective immunity when a patient is challenged, as it does not account for any cell-mediated immunity present, virulence of the virus strain or dose of viral challenge; however, none of these are easily measured or predicted, so serological titres are used in lieu of more accurate determinations.

Laboratory-based methods assessing antibody function (e.g. haemagglutination inhibition assays, serum neutralisation assays) are considered the gold standard. They have been used to measure the humoral immune response to vaccination, and by correlating measured antibody titre to experimental challenge data, so-called protective titres have been defined for some pathogens (e.g. canine parvovirus, canine distemper virus). More recently, simple in-practice serological tests have become available for some of the core vaccines (CDV, CPV, CAV, FHV, FCV and FPV) and these measure antibody level (not function).

MDA immunity protects neonates against diseases from birth until the MDA blood levels decrease to an insufficient level. Whilst MDA can provide protection against disease, high titres can also interfere with immunisation. In most cats and dogs, titres will decrease below this interfering level around 8 to 12 weeks of age,⁹ but it is likely that a small proportion of young animals will have MDA that will last until 16–20 weeks of age.² MDA levels are dependent on the neonate consuming sufficient MDA-containing colostrum shortly after birth. MDA can interfere with vaccination and prevent adequate seroconversion. Vaccination failures have been documented in Australia and the highest risk for canine parvovirus vaccination failure was identified in puppies receiving a last vaccination before 16 weeks of age.¹⁰ When the MDA level has reduced, the neonate is at risk of disease unless successful active immunisation from vaccination is achieved.^11,12,13

Herd immunity is not a concept that is used frequently in small animal medicine. The vaccination of the individual pet animal is important not only for the protection of the individual but also to reduce the number of susceptible animals in the regional population and thus the prevalence of the disease.²

Scientific information suggests that the DOI delivered by many of the available vaccines (based on either serological titres or challenge experiments) is variable, but in most animals DOI for the core vaccine components is significantly longer than 12 months (and often greater than 3 years) and for non-core vaccine components is often 12 months or less. This information has been refined in the 2015 World Small Animal Veterinary Association (WSAVA) guidelines suggesting a triennial core vaccination schedule and personalised non-core vaccination schedule.

It is worth noting that extended DOI (> 12 months) for the core vaccine components may not persist for all vaccinated patients, with scientific evidence showing that 1.3–5% of animals at least 1–3 years from last vaccination do not carry sufficient antibody titres to suggest protection against canine parvovirus^5,6,14,15 and 0.4–3.5% of dogs being non-serological responders to one of the core vaccine components.^5,6 These facts should be taken into consideration when tailoring a vaccination protocol, particularly in high-risk disease locations.

With the incidence of some of the life-threatening infectious diseases becoming very low in some regions in Australia, the need to adhere to strict vaccination protocols has been questioned. However, disease outbreaks and epidemics still occur, and risk may vary considerably depending on region. Canine parvovirus risk in Australia, for example, has been shown to be significantly higher in rural than urban areas¹⁶ and is associated with areas of relative socioeconomic disadvantage,¹⁷ which may necessitate greater precaution with vaccination in these regions.

Guidelines

The Vaccination Guideline Group (VGG) of the WSAVA recommends that vaccines be defined as core, non-core or not recommended.² Core vaccines should be administered to all animals to protect them against severe, life-threatening diseases that have a global distribution. Non-core vaccines are required only by those animals whose geographic location, local environment or lifestyle places them at risk of contracting specific infections. Not recommended vaccines are those that have insufficient scientific evidence to justify their use.

Table 1. WSAVA VGG 2015 vaccination groupings*

* Vaccines unavailable in Australia are not displayed

The AVA supports vaccination schedules that recognise that requirements for vaccination will differ based on the individual patient, situation and veterinarian–client–patient relationship. As such, it is not possible to give prescriptive guidelines for vaccinating dogs and cats.

The AVA supports administration of core vaccines to all companion animals to protect them against severe, life-threatening diseases that have a global distribution. Vaccines with extended DOI (e.g. triennial) may be used for core vaccination in adult cats and dogs where risk of disease does not necessitate more frequent revaccination; however, local animal and environmental factors, including but not limited to increased risk of infection (e.g. increased incidence in the population, upcoming boarding) and acknowledged lack of sterile immunity with some core vaccines (e.g. feline herpesvirus 1 and feline calicivirus) may dictate a more traditional annual core vaccination schedule in some situations.

Serological (titre) testing can be considered as a method of evaluating immunity, but as noted above it does not fully reflect protective immunity because it does not account for any cell-mediated immunity present, virulence of the virus strain or dose of viral challenge. Also interpretation of these serological (antibody) tests varies depending on the test methodology (reference laboratory vs in-clinic), how the result is to be used (e.g. determining vaccination status, determining seroconversion post-initial vaccination schedule, determining need for revaccination, shelter management) and the particular infectious agent being assessed in terms of antibody response (e.g. canine parvovirus vs feline herpesvirus). Hence prescriptive recommendations are not part of this policy. The following references provide further useful information when deciding on appropriate patient management.^4,5,8,18,19

Puppy and kitten core vaccinations are vitally important in preventing disease. Because of the variability in the level and duration of MDA among individual animals, core vaccines must be administered to puppies and kittens, from 6 to 8 weeks of age, then every 2–4 weeks with timing of the final dose being not earlier than the age of 16 weeks.^2,10 Although some canine vaccines have label claims for a 10-week finish to a puppy vaccination protocol, it is still considered good practice to use a 16-week vaccination if any unacceptable environmental risks exist for the young dog.¹⁰

In disease outbreak situations, regardless of age, any animals that are not fully immunised must be kept isolated from at-risk areas for disease until at least 7–14 days after vaccination, which is considered the minimum time for seroconversion to occur.²⁰ In neonates, this means isolation from at-risk areas until at least 7–14 days after final (16 week) neonatal vaccination. Puppy preschool properly conducted in a clean environment should not pose a risk to a puppy that is yet to receive its full course of vaccinations.²¹

A subsequent ‘adult’ booster vaccine has traditionally been administered approximately 12 months after the last puppy or kitten vaccine, but recent WSAVA VGG guidelines now recommend this subsequent booster may be given from 6 months of age.² This will help catch the small proportion of patients that failed to respond to the previous vaccination and will reduce the risk of disease for these patients in at-risk environments.

An annual health check is strongly recommended, even if animals are not to be vaccinated. Revaccination recommendations should aim to create and maintain clinically relevant immunity while minimising the potential for adverse reactions.

The use of vaccines in the animal shelter environment presents unique challenges in achieving an optimum level of protection, given the animals are often highly susceptible and shelters may operate within significant financial constraints. The absolute minimum vaccination protocol in this situation would be a single administration of core vaccines at or before the time of admission to the shelter. For puppies and kittens in high-risk shelters, ideally, and where funding permits, vaccination should start at 4–6 weeks of age and be given every 2 weeks until 16–20 weeks of age.^2,18 The AVA considers that all shelters should aim to vaccinate puppies and kittens every 2 weeks until 16–20 weeks of age.

Non-core vaccines target diseases that are a risk in a limited geographic region or are a relative risk because of the lifestyle of the pet. The decision to use non-core vaccines is made for individual pets based upon the particular requirements of the individual and in consultation between the veterinarian and client. Many non-core vaccines require annual vaccination.

At the time of vaccine administration the following information should be recorded in the patient’s permanent medical record:

• date of vaccination
• identity of person administering the vaccine
• vaccine brand, batch number and expiry date
• site and route of administration.

Informed owner consent is important when vaccination protocols are used ‘off label’.

Any adverse event should be reported, identifying the product, batch, animal and reaction involved, to the manufacturer or the Australian Pesticides and Veterinary Medicines Authority (APVMA) Adverse Experience Reporting Program.

References

1. Klingborg DJ, Hustead DR, Curry-Galvin EA et al. AVMA Council on Biologic and Therapeutic Agents’ report on dog and cat vaccines. JAVMA 2002;221:1401–1407.
2. Day MJ, Horzinek MC, Schultz RD et al. WSAVA Guidelines for the vaccination of dogs and cats. J Small Anim Pract 2016;57:E1–45.
3. Australian Pesticides and Veterinary Medicines Authority. Adverse Experience Reporting Program for Veterinary Medicines: definition of an adverse experience. APVMA, 2017. https://apvma.gov.au/node/309. Accessed November 2017.
4. Lappin M, Andrews J, Simpson D et al. Use of serologic tests to predict resistance to feline herpesvirus 1, feline calicivirus, and feline parvovirus infection in cats. JAVMA 2002;220:38–42.
5. Mitchell SA, Zwijnenberg RJ, Huang J et al. Duration of serological response to canine parvovirus-type 2, canine distemper virus, canine adenovirus type 1 and canine parainfluenza virus in client-owned dogs in Australia. AVJ 2012;90:468–473.
6. Mouzin DE, Lorenzen MJ, Haworth JD et al. Duration of serologic response to five viral antigens in dogs. JAVMA 2004;224:55–60.
7. Mouzin DE, Lorenzen MJ, Haworth JD et al. Duration of serologic response to three viral antigens in cats. JAVMA 2004;224:61–66.
8. Roth J, Spickler A. Duration of immunity induced by companion animal vaccines. Anim Health Res Rev 2010;11:165–190.
9. Pollock RVH, Carmichael LE. Maternally derived immunity to canine parvovirus infection: transfer, decline, and interference with vaccination. JAVMA 1982;180:37–42.
10. Altman KD, Kelman M, Ward MP. Are vaccine strain, type or administration protocol risk factors for canine parvovirus vaccine failure? Vet Microbiol 2017;210:8–16.
11. Buonavoglia C, Tollis M, Buonavoglia D et al. Response of pups with maternal derived antibody to modified-live canine parvovirus vaccine. Comp Immunol Microbiol Infect Dis 1992;15:281–283.
12. Pardo MC, Tanner P, Bauman J et al. Immunisation of puppies in the presence of maternally derived antibodies against canine distemper virus. J Comp Pathol 2007;137:S72–75.
13. Wilson S, Siedek E, Thomas A et al. Influence of maternally-derived antibodies in 6-week old dogs for the efficacy of a new vaccine to protect dogs against virulent challenge with canine distemper virus, adenovirus or parvovirus. Trials Vaccinol 2014;3:107–113.
14. Böhm M, Thompson H, Weir A et al. Serum antibody titres to canine parvovirus, adenovirus and distemper virus in dogs in the UK which had not been vaccinated for at least three years. Vet Rec 2004;154:457–463.
15. Riedl M, Truyen U, Reese S et al. Prevalence of antibodies to canine parvovirus and reaction to vaccination in client-owned, healthy dogs. Vet Rec 2015;177:597.
16. Zourkas E, Ward MP, Kelman M. Canine parvovirus in Australia: A comparative study of reported rural and urban cases. Vet Microbiol 2015;181:198–2013.
17. Brady S, Norris JM, Kelman M et al. Canine parvovirus in Australia: the role of socio-economic factors in disease clusters. Vet J 2012;193:522–528.
18. Ford R. Antibody titres vs. vaccination. Today’s Vet Pract 2013;May/June:57–60.
19. Abdelmagid OY, Larson L, Payne L et al. Evaluation of the efficacy and duration of immunity of a canine combination vaccine against virulent parvovirus, infectious canine hepatitis virus, and distemper virus experimental challenges. Vet Ther 2004;5:173–186.
20. Decaro N, Crescenzo G, Desario C et al. Long-term viremia and fecal shedding in pups after modified-live canine parvovirus vaccination. Vaccine 2014;32:3850–3853.
21. Stepita ME, Bain MJ, Kass PH. Frequency of CPV infection in vaccinated puppies that attended puppy socialization classes. J Am Anim Hosp Assoc 2013;49:95–100.

    Ford RB, Larson LJ, Schultz RD et al. 2017 AAHA Canine Vaccination Guidelines. J Am Anim Hosp Assoc 2017;53:243–251.