ABSTRACT: Vaccines used routinely for canine vaccination include modified live vaccines (MLVs) and killed vaccines. MLVs have higher immunogemcity than killed vaccines meaning that they are more successful at eliciting an immune response Studies into the duration of immunity (DOI) of MLVs have helped introduce the extended revaccination interval of three years and many vaccine manufacturers have now relicensed their products for such use. Although suspected adverse reactions (SARs) to vaccination are rare, extended revaccination intervals should help reduce the number seen in practice. It is important to be aware of the possible reactions and to ensure these are reported appropriately. Vaccine failure is rare but may arise owing to poor response on the part of the individual, the presence of maternally derived antibodies [MDA] and environmental factors, such as inappropriate vaccine storage. The Vaccination Guidelines Group (VGG) recommendations cover the issue of maternally derived antibodies (MDA), extended revaccination intervals and the use of serology to determine whether a booster is needed.

Introduction

In line with the recommendations of the Vaccination Guidelines Group (VGG),1 there have been changes to the way in which dogs are vaccinated in the United Kingdom. Protocols have moved away from revaccinating for all diseases every year; instead, many manufacturers have now relicensed their vaccines for administration every three years for the core diseases.

The VGG classifies distemper (CDV), hepatitis (CAV-1) and parvovirus (CPV) as core diseases, and parainfluenza and leptospirosis as non-core diseases. Non core diseases have retained annual revaccination.

As these new protocols are becoming increasingly popular in veterinary practice, nurses must be aware of the changes should they be faced with owners questioning why protocols have changed.

Vaccine types

Attenuated or modified live vaccines

Attenuation describes the processes used to reduce the virulence of the antigens included in a vaccine, whilst preserving them in a way that maintains effectiveness without risking serious disease.2 However, there may be a risk that antigens in these vaccines can revert to becoming virulent, causing clinical signs of disease.3

However, these vaccines can initiate a prolonged immune response and may be described as having higher immunogenicity (the ability to initiate an immune response). These are the type of vaccines used to protect against the core diseases.

Killed or inactivated vaccines

Killed vaccines are used to protect against the non-core diseases, such as leptospirosis (serovars L. icterohaemorrhagiae and L. canicola) and parainfluenza. A lasting immune response is not possible because of the processes used to completely inactivate the antigens, so annual revaccination is needed.4

An adjuvant is added to enhance the vaccines ability to initiate an immune response.5 These have, however, been associated with allergic reactions.3

Duration of immunity

DOI describes the time period when a vaccine-specific immune response is present.6 Evidence provided by relatively recent research has proven that these are longer than previously thought for the majority of dogs; indeed, some dogs have shown an immune response 15 years after vaccination.7

In light of such evidence, tri-annual revaccination for the core diseases is now recommended where MLVs are used, but the dog must receive the first annual booster.1 Recommended revaccination intervals for leptospirosis (serovars L. icterohaemorrhagiae and L. canicola) and parainfluenza remain annual as killed vaccines provide shorter protection intervals.

This regimen also ensures that veterinary surgeons are seeing dogs annually, enabling new protocols to be explained to owners and ensuring compliance.8 It is also important for veterinary nurses to spend time with owners to ensure that they understand the changes to the vaccination protocols used (Figure 1).

Figure 1: It is important for nurses to understand the mechanism of vaccinations so that they can explain this vital preventive measure to owners to ensure maximum compliance. (Image courtesy of Laura Daniels) 

Do all dogs respond in the same way?

Individual dogs will respond differently to vaccination.2'4’9'10-11’12 Although breed appears to have an influence on response, there are currently insufficient data to support this on an individual basis. Severe hypertrophic osteodystrophy has been noted in some Weimaraner puppies after administration of MLV vaccines.4 

As this condition usually manifests itself 10 days post-vaccination, it is usually easy to link it to the vaccine.

All distemper vaccines are MLVs and this justifies the need for a thorough risk/benefit assessment when vaccinating these puppies. Weimaraners have also been linked to inflammatory disease and recurrent bacterial infection after vaccination, as well as significantly lower titres of a specific antibody involved in vaccine responses.11

It would also appear that the German shepherd dog is a poor responder to vaccination.2 There is evidence of immunomodulation in this breed.12 This is where cell-mediated immunity decreases and humoral immunity increases after vaccination. Dogs infected with subclinical and opportunistic disease may become infected, but this shift in immunity is not permanent.

Again, this reinforces the need for a thorough health check at the time of vaccination to identify any subtle signs of disease. The research that highlighted this only used MLVs, so it may be possible that not all vaccine types cause this response in German shepherd dogs.

Another common breed that is associated with poor vaccine responses is the Rottweiler.2 Some puppies have been shown to have low levels of two antibodies involved in vaccine responses, along with signs of systemic and inflammatory skin disease.9 There have been suggestions that these conditions are the result of a complex immune system abnormality, rather than a simple link with low titres.9

Age may affect immune responses. Data appear to demonstrate that dogs under six months old have lower titres after rabies vaccination.13 However, no similar research has been carried out focusing on the core diseases.

This is not an exhaustive list, but it is intended to give nurses some idea of the breeds that may not respond appropriately to vaccination.

Suspected adverse reactions

Vaccination is the safest method of protecting dogs from infectious diseases, especially when compared with exposure to natural infection. Although Suspected adverse reactions (SARs) related to vaccination are frequently discussed, they are rarely formally reported, possibly because they are often non-specific and not easily linked to the vaccine.14

The possibility of SARs
is not a valid reason for not vaccinating dogs, as the number of affected dogs is relatively small when compared to the number of dogs vaccinated as shown by annual* SAR publications.15'16- 17,18'19,20

Transient post-vaccinal, non-specific illness (TPVNSI) has been noted in dogs in the two weeks following vaccination21. The clinical signs include pyrexia, lethargy, anorexia and lymphadenopathy.2 Nurses should be aware of these when dealing with the concerned owner because this could affect the owners future attitude to vaccination.14

Allergic reactions to vaccines have also been reported in dogs. These have been split into two categories. The first category includes classical anaphylaxis,22 which usually occurs within an hour of MLV and combined vaccine administration.23 The second category includes dermatological signs, such as facial oedema, pruritus and erythema.22

There has been some suggestion that the use of foetal calf serum in vaccines is associated with allergic reactions,23 and may increase atopic and dietary sensitivities.2

Tissue inflammation can occur at the vaccine administration site although this is rare.2 A more common, associated problem is the incidence of fibrosarcoma in cats. However, one of the authors has seen a case of an impressive degree of tissue inflammation following vaccination in a Bull Mastiff puppy.

Nurses can help in the identification of possible vaccine-related SARs by being aware of the various types of reaction.

A well-informed practice team is more likely to be in a position to provide an accurate indication of the prevalence of these reactions.

Maternally derived antibodies and vaccine failure

The presence of the antibodies that puppies receive from the dams milk is an important consideration when vaccinating puppies as, whilst MDA is essentia] for survival, it can cause vaccine failure.4 It is thought that this could be by three different mechanisms as represented by (Figures 2-4).

Figure 2: Neutralisation of vaccinal antigen by MDA 

Figure 3: MDA binding with B-lymphocyte 

Figure 4: MDA disguising the receptor of a vaccinal antigen

MDA may neutralise antigens rapidly so that fewer antigens are presented to B-lymphocytes.4 This means that the immune system cannot begin to initiate a response (Figure 2).

MDA may bind to receptors on B- lymphocytes meaning that antigens cannot bind with them.4 Binding is essential for an immune response to be produced (Figure 3).

It is also thought that MDA could disguise parts of the vaccinal antigens, making them unrecognisable to the immune system (Figure 4).4

There is some debate as to whether to use vaccine programmes that allow for an earlier finish for socialisation and behavioural benefits, or to use a later finish programme to overcome the potentially negative effects of MDA.

MDA usually decreases by at least 12 weeks of age, although it may still be present in some puppies at 16 weeks of age.1 It is, therefore, recommended that a third vaccination is added to vaccine courses, which is given at 16 weeks to cover those puppies that still have MDA present at this time.1

Figure 5 indicates the suggested primary vaccination protocol in relation to MDA decay in the majority of puppies between eight and 16 weeks of age.

Figure 5: MDA decay in the majority of puppies and the vaccination protocol recommended by the VGG 

Other causes of vaccine failure

It is possible for practical factors to cause vaccine failure.1 An important responsibility of the veterinary nurse is to ensure that the refrigerator is maintained at an appropriate, constant temperature – for most vaccines this is 2-8°C. It is also recommended that vaccines are protected from light. 

These requirements are in place to maintain antigen preservation.4 The fridge door shelves are unsuitable for storage because they are exposed to temperature fluctuations when the door is opened and closed.

Different vaccine manufacturers recommend various time limits for administration of reconstituted vaccines; but ideally they should be used immediately as this lowers the risk of failed antigen preservation. Use of vaccines that have been reconstituted for longer than the recommended time frame, risks failure and may be viewed as negligent.

When checking stock, the veterinary nurse should also ensure that vaccines have not exceeded expiry dates, as to ignore this will also lead to vaccine failure.

Vaccination may be unsuccessful in initiating an immune response if the animal is already infected, b
ecause a compromised immune system cannot respond to the vaccinal antigens appropriately. It is, therefore, of great importance that thorough health checks are completed prior to vaccination to ensure that the status of the individual predisposes to stimulation of appropriate levels of immunity.

Conclusion

Veterinary nurses must be able to discuss vaccination with owners, although ultimately the decision as to which protocol is used lies with the veterinary surgeon. The Vaccination Guidelines Group recommendations make for interesting reading and will provide a comprehensive explanation of topics touched upon in this article – a reference has been included for those who would like to read more. As outlined in the article, not all dogs will respond in the same way to vaccination; so serological testing could be used to create tailored vaccination programmes for individual dogs, and this will be discussed in a subsequent article. 

Author(s)

Bethaney Heayns BSc(Hons) RVN 

Bethaney Heayns qualified as a RVN in 2008 and graduated with a First Class Honours Degree from Harper Adams in 2009. This article was completed when Bethaney worked as a research assistant at Harper Adams. She is now based at the Royal Veterinary College as a clinical investigation nurse.

Stephen Baugh BSc(Hons) BVM&S MRCVS

Steve Baugh is programme manager for the Animals Degree courses and a senior lecturer at Harper Adams.

To cite this article use either

DOI: 10.1111/j.2045-0648 2012.00160.x or Veterinary Nursing Journal Vol 27 pp 133-136

References

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9.   DAY. M. (1999) Possible immunodeficiency in related Rottweiler dogs. Journal of Small Animal Practice. 40: 561-568.

10.   COYNE, M J. (2000) Efficacy of Two Canine Parvovirus Vaccines for Inducing Seroconversion in Rottweiler and Doberman Pinscher Pups with Various Levels of Maternally Derived Antibodies. Veterinary Therapeutics. 1(1): 35-42.

11.   FOALE, R. D„ HERRTAGE. M. E.. and DAY. M. J. (2003) Retrospective study of 25 young Weimaraners with low serum immunoglobulin concentrations and inflammatory disease. Veterinary Record. 153: 553-558.

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13.   MANSFIELD, K. L„ BURR, P. D.. SNODGRASS, D. R.. SAYERS. R.. and FOOKS. A. R. (2004) Factors affecting the serological response to dogs and cats to rabies vaccination. Veterinary Record. 154(14):423-426.

14.   O'ROURKE. D. (2008) The practitioner's role in SAR reporting. In Practice. 30: 398-402.

15.   DYER. F„ MULUGETA. R., SPAGNUOLO-WEAVER. M„ and TAIT, A. (2005) Suspected adverse reactions. 2004. Veterinary Record. 156: 561-563.

16.   DYER, F.. MULUGETA, R„ SPAGNUOLO-WEAVER. M., and TAIT. A. (2006) Suspected adverse reactions. 2005. Veterinary Record. 158: 464-466.

17.   DYER. F.. SPAGNUOLO-WEAVER. M„ COOLES, S. and TAIT. A. (2007) Suspected adverse reactions. 2006. Veterinary Record. 160: 748-750.

18 DYER. F„ SPAGNUOLO-WEAVER. M„ COOLES. S. and TAIT, A. (2008) Suspected adverse reactions, 2007.   Veterinary Record. 163: 69-72.

19.   DYER. F.. BROWN. E.. COOLES. S. and TAIT, A. (2009) Suspected adverse reactions, 2008. Veterinary Record. 165: 162-164.

20.   DYER. F„ DIESEL. G.. COOLES, S. and TAIT, A. (2010) Suspected adverse reactions, 2009 Veterinary Record. 167: 118-121.

21.   EDWARDS. D. S., HENLEY, W. E.. ELY, E. R. and WOOD, J. L. N. (2004) Vaccination and ill-health in dogs: a lack of temporal association and evidence of equivalence. Vaccine. 22: 3270-3273.

22.   OHMORI. K„ SAKAGUCHI, M.. KABURAGI. Y., MAEDA, S.. MASUDA, K.. OHNO, K. and TSUJIMOTO, H. (2005) Suspected allergic reactions after vaccination in 85 dogs in Japan. Veterinary Record. 156: 87-88.

23.   OHMORI. K.. MASUDA. K„ DEBOER, D. J.. SAKAGUCHI, M„ and TSUJIMOTO. H. (2007) Immunoblot analysis for IgE-reactive components of fetal calf serum in dogs that developed allergic reactions after non-rabies vaccination. Veterinary Immunology and Immunopathology. 115:166-171.

Further reading

DAY, M. J. (2006) Vaccine side effects: Fact and fiction. Veterinary Microbiology 117: 51-58.

• VOL 27 • April 2012 • Veterinary Nursing Journal