All over the world, there is more or less consensus that we should vaccinate our dogs against certain diseases. Below, I will write about research and decisions that form the basis of this consensus, which diseases the dogs are vaccinated against, as well as the benefits and potential problems with vaccinations of dogs. As will be shown below, there are some serious disadvantages of vaccination, especially regarding the amount of vaccine and how often the dogs are vaccinated. In this context, small dogs are more vulnerable than large dogs.

Since I live in Sweden, I will have references to the Swedish recommendations besides the global ones.

Who suggests which vaccinations our dogs should take?

WSAVA, The World Small Animal Veterinary Association, is a worldwide association that assembles veterinarians from countries from all over the world. They play an important role for guidelines in animal welfare questions like vaccination routines for the member countries. They have 67 member countries, among them Sweden, and 10 associate countries. (See their webpage Thus, they are a central actor in the field of vaccination recommendations and the one most countries follow.

WSAVAs Vaccination Guidelines Group (VGG) consists of scientists who have done research in the field of vaccination and thus know the field thoroughly.

In WSAVAs “Guidelines for the vaccination of dogs and cats”, they single out three vaccines as “core vaccines” with which all dogs should be vaccinated. The vaccines are those against the canine distemper virus (CDV), the canine adenovirus (CAV; hepatitis contagiosa canis (HCC), and canine parvovirus type 2 (CPV-2). Besides the core vaccines, they also have defined “non-core vaccines” which are related to geography, environment and lifestyle. Regarding the non-core vaccines they write that there should be an assessment of the risks and the benefits of it, i.e. which is the greater risk – that the dog is unprotected, or that it might have negative reactions from the vaccination. Vaccination against rabies is a non-core vaccine since it is not prevalent in all countries, but it is core in the countries where the illness is found.

In Sweden, the National Veterinary Institute (Statens veterinärmedicinska anstalt (SVA)) has given guidelines for core vaccination of dogs (and cats) (Windahl and Ingman 2009). They relate to the “Guidelines for the vaccination of dogs and cats” and agree on the three core vaccines that WSAVA has pointed out. Although SVA does not suggest that Swedish dogs should be vaccinated against parainfluenza this is most often done in Sweden, since the vaccine preparation that “all” Swedish dogs get as puppies and every three years contains vaccine not only of the three core vaccines, but also a vaccine against parainfluenza (Nobivac DHPPi).

How often does a dog have to be vaccinated with the core vaccines?

In the first issue in 2006 of the Swedish journal Svensk veterinärtidning, Johan Beck-Friis published an article about an international scientific symposium in Autumn 2005 about vaccination routines for dogs and cats. At this time veterinarians routinely vaccinated dogs (and cats) yearly and the scientists at the symposium said that this had to change. Professor Marion Horzinek, at that time the chair of WSAVAs Vaccination Guidelines Group (VGG), said in his lecture that the yearly vaccination routines had no scientific foundation. He also maintained that, whereas we vaccinate many animals too often, there are others that do not get any protection at all. He stated that when a population reaches about 70% of vaccinated individuals, the illness does usually not occur.

Horzinek’s colleague professor Ronald Schultz, also a member of the VGG, said that modern vaccines have shown to give protection up to seven years after the first core vaccination. Schultz had done research with core MLV (modified live virus) vaccinations against canine distemper virus (CDV), the canine adenovirus (CAV), and canine parvovirus type 2 (CPV-2) and he found that the protection against these viruses lasted for at least seven years (Beck-Friis 2006: 40, my italics).

Schultz et al:s later research also supports his conclusion at the conference, that the protection is very long lasting. In a study published in 2010 Schultz et al. write that “The longest period of time after initial vaccination that dogs were sampled and that antibody was found to persist was 14 year for CDV […], 14 years for CAV-1 […] and 10 years for CPV-2”. In environments free from CDV and CPV-2 they had “not been able to keep dogs for longer than 9 years”, and in those environments they had antibodies against CDV, CAV-1 and CPV-2 during those 9 years. He also refers to a study that showed antibodies for at least 4,5 years. The dogs in the study, “when challenged, were completely protected” (Schultz et al. 2010: 106). Another study showed that the response to challenges of CDV, CAV-1 and CPV-2 was the same disregarded of age of the dogs. Regarding the “duration of immunity (DOI) Schultz concludes: “all studies based on persistence of antibody as well as challenge show that immunity to CDV, CPV-2 and CAV-1 persists for a lifetime after vaccination, similar to the persistence of immunity after natural infection” (Schultz et al. 2010: 106).

In spite of the above conclusion in Schultz et al:s research, in the WSAVA “Guidelines for the vaccination of dogs and cats” from 2010 and from 2016, this result is not spelled out. They write that “Dogs that have responded to vaccination with MLV core vaccines maintain a solid immunity (immunological memory) for many years in the absence of any repeat vaccination” (referring to four studies). And further that, after the booster, “subsequent revaccinations are given at intervals of 3 years or longer” [my italics] (Day et al. 2016: 8). They do write repeatedly about the longer duration of immunization but they do not tell how long it has shown to be in their studies. Therefore, the guidelines do not fully correspond to the results of their research.

In the guidelines, the VGG recommends that dogs get the ”initial core vaccination at 6–8 weeks of age, then every 2–4 weeks until 16 weeks of age or older”. Thus, the recommendation is that a puppy is vaccinated 3–6 times when it is 6–16 weeks old. When I look at the same guidelines from 2010, the recommendation is instead “initial vaccination at 8 – 9 weeks of age followed by a second vaccination 3 – 4 weeks later, and a third vaccination given between 14–16 weeks of age” (Day et al. 2010: 344). Thus, in the new guidelines, the group opens for a double amount of vaccinations of the puppy as compared to the guidelines of 2010. In the guidelines for core vaccination of the Swedish National Veterinary Institute (2009) the authors refer to WSAVAs recommendation to vaccinate puppies three times between 8 and 16 weeks. The National Veterinary Institute does not recommend the third of these vaccinations since “no big outbursts of disease has been seen in the country with the present recommendations” (“då inga stora sjukdomsutbrott har setts i landet med de nuvarande rekommendationerna”) (Windahl and Ingman 2009: 52).

Since the puppy naturally has a passive immunity received from its mother (maternally-derived antibody, MDA) during the first 8–12 weeks of life, as long as this immunity is present, it is not possible to activate the immune system with vaccines. The VGG writes that some puppies may have poor MDA and I suppose this is the reason why they want the puppy to be regularly vaccinated during the first 6–16 weeks. They also see a risk that the puppy did not get the immunization from these first vaccinations after all, probably because they reckon with an active MDA in some puppies even in the 16th week. Therefore, they want the dog to get a booster later in its first year.

In the guidelines of 2010 the group recommends that the dog gets a booster vaccination at the age of 12 months (Day et al. 2010: 344). However, in the guidelines of 2016 this is changed, and the scientists instead recommend that the booster is given at six months old. The aim of the “booster” is “to ensure that a protective immune response develops in any dog that may have failed to respond to any of the vaccines in the primary core series, rather than necessarily ‘boosting’ the immune response” (Day et al. 2016: 8). The reason given for giving the “booster” earlier is that there is a risk that the puppy is unprotected longer if it did not get immunization from the first vaccinations.

As it looks, to calm the veterinarians who fear that they will not be allowed to call their patient at one years old, the guidelines of 2016 say:

“This new recommendation for vaccination at 6 months of age as an alternative to vaccination at about 1 year of age is certainly not mutually exclusive to, and does not preclude, a 1-year or 16-month ‘first annual health check’. Many veterinarians are understandably keen to check the animals under their care at around the time they reach skeletal maturity.” (Day et al. 2016: 8)

After the 6 or 12 month booster, the VGG recommends that “subsequent revaccinations are given at intervals of 3 years or longer” (Day et al. 2010: 344; id. 2016: 8). In spite of this, “an adult dog may today still be revaccinated annually”, according to both the 2010 and the 1016 guidelines, since there are vaccinations that are not core that can be given, such as those against Borrelia and parainfluenza (and which do not give life-long immunization).

In 2010, the group recommends that the manufacturers of vaccines make solutions with only one of the three core vaccinations present in one dose (Day et al. 2010: 344; id. 2016: 8). In 2016, this recommendation is altered in the following way: “The VGG would encourage manufacturers to make a full range of reduced-component vaccines (or at least separate core and non-core vaccines […]) available wherever possible” (Day et al. 2016: 8). Thus, in this question, as in the question of number of vaccinations of puppies, the VGG has changed their mind in a direction that leads to a heavier “vaccination load” on the dogs and more profit for the vaccine manufacturers.

My impression when I read the recommendations of WSAVA as well as the research done of the members of the VGG is that the group has to find compromises between several interests in their recommendations, which is also expressed in this citation:

“The VGG faces the difficult challenge of setting a middle-course through various national or regional guidelines. Its recommendations attempt to provide a balanced perspective to account for global differences in the keeping of small companion animals.” (Day et al. 2016: 5)

Besides the differences globally in guidelines, there are also large multinational vaccine producers who want to sell as many vaccine doses as possible. There are probably also veterinarians who think that their income will decrease if pet owners vaccinate their pets less often. Furthermore, there are pet owners who do not have their pets vaccinated if they find it too expensive. There is also the research done by themselves that they want to take into account. Regarding the difference globally in guidelines, I can imagine that among some people, there is a resistance to reduce the vaccine load because of habit and lack of knowledge. I see the three-year recommendation as a compromise considering all these actors.

What are the risks with not vaccinating your dog?

The parainfluenza virus is not life-threatening for a healthy dog, adult or puppy and only gives mild to moderate symptoms (E.g. Sykes 2014: 172; Dodds 2017). (To note is, that the so-called “kennel cough” is caused by more than one pathogen and some of these pathogens can cause severe symptoms. These pathogens are not covered by the parainfluenza vaccination (See Dodds 2017)). However, the health and life of puppies are threatened by CDV, CAV-1 and CPV-2. In adult dogs, the symptoms are usually mild or even missing but if they are infected or carry the CDV, CAV-1 or CPV-2 virus, they can infect puppies. Therefore, the scientists maintain that it is essential that all dogs are vaccinated against these viruses. As was pointed out above, when a population reaches about 70% of vaccinated individuals, the illness usually does not occur. This means that every vaccinated dog contributes to the elimination of the diseases in the whole population (Day et al. 2016: 6).

CDV: transmission routes and symptoms in puppies
CDV is transmitted between dogs through contact with body secretion from infected dogs. In an adult dog, it might not even be seen that it is infected. Virus is mostly exuded from all bodily secretes a couple of weeks but it can be exuded as long as 90 days. Virus does not survive for long in indoor temperature and it dies in heat. In cold climates, it can survive several weeks. In tissue, it can survive at least three hours at 20ºC and at least one hour at 37 ºC (SVA about distemper).

An infected puppy commonly get damages in the central nervous system, airway epithelium, and it can give secondary infections because the virus is immunosuppressive. This serious infection of CDV with high mortality is mainly found in puppies at three to six months of age (SVA about distemper), i.e. when the maternally-derived antibody has disappeared and before the immune system is fully mature (reference needed).

CPV-2: transmission routes and symptoms in puppies
The parvovirus is spread through feces and oral secretes. The virus is exuded in the feces about three to four days after infection and can continue another two weeks. The dog can carry and spread it from the fur and the paws even longer than that. This virus can continue to live outdoors both in the nature and in the city up to several years. In addition, humans can spread it if it has come on shoes, clothes or hands (SVA about parvo virus).

An infected puppy gets cell necrosis in bone marrow, lymphoid tissue and in the crypt cells of the intestines, which leads to diarrhea and decreased numbers of white blood cells. Newborn puppies without maternally-derived antibody usually die from the disease (SVA about parvo virus).

CAV-1: transmission routes and symptoms in puppies
Infectious hepatitis in dogs is spread above all through the urine of an infected dog and during the first two weeks also from other body fluids. The virus can be found in the urine up to 6 – 9 months or even longer. A dog can get in contact with the virus through another dog and its urine. Other transmission routes are contaminated environments indoors and outdoors as well contaminated hands and clothes. The environment and carriers without symptoms are the most common source of contamination. The virus survives several weeks in both warm and cold environments (SVA about infectious hepatitis).

An infected puppy gets a severe systemic disease with affected liver and kidneys. There can be neurological symptoms, edema and diarrhea and it often dies within a few hours. A bitch who is infected (with or without symptoms) with CAV-1 during her gestation gives birth to stillborn puppies or puppies who die soon after being born (SVA about infectious hepatitis).

Are there any risks with vaccinations?

Most dogs only get the wanted result of a vaccination, i.e. a protection against a disease. However, there are risks with vaccinations, at least for some dogs. That there are potential risks with vaccinations is mentioned in VGGs “Guidelines for the vaccination of dogs and cats”:

“A second major concept regarding vaccination of dogs and cats has been the recognition that we should aim to reduce the ‘vaccine load’ on individual animals in order to minimize the potential for adverse reactions to vaccine products and reduce the time and financial burden on clients and veterinarians of unjustified veterinary medical procedures.” (Day et al. 2016: 6)

Besides that, and the mention that the risks and benefits of vaccinating with non-core vaccines should be assessed for every individual, the guidelines do not discuss risks with vaccines further. The only risk that is mentioned recurrently is exposure to the viruses.

In an article in the Swedish journal Svensk veterinärtidning three veterinarians describe the side effects of vaccines, anthelmintics and antibiotics that was reported to the Swedish Medical Products Agency (Läkemedelsverket) during 2015. Here I will only focus on the side effects of vaccines.

During the relevant year, there were 81 reports of side effects of vaccines. Most of the side effects of vaccines against canine distemper virus (CDV), the canine adenovirus (CAV-1), canine parvovirus type 2 (CPV-2) and parainfluenza (Nobivac DHPPi contains vaccines against these four viruses) were anaphylactic reactions, i.e. allergic reactions that appear suddenly. This usually shows as swelling around nose and eyes and this affects the breathing system. Several dogs also got an anaphylactic shock with pale mucous membranes and impaired consciousness (Tjälve et al. 2016: 18). The anaphylactic shock can be life-threatening if not immediately treated. The authors concludes regarding the reported frequency of side effects in relation to sold doses that the side effects fall within the frequency “less common side effects” (Tjälve et al. 2016: 18). It would be interesting to see a study about the frequency of reports from the veterinarians regarding side effects from vaccination as well as whether there is an underdiagnosing of these side effects.

The authors enumerate the dog breeds that were the most common among those who got side effects, and Chihuahua lies on top with nine individuals, followed by pug and Tibetan spaniel with three individuals each. Furthermore, two miniature wire-haired Dachshunds and two Bearded collies were among the individuals with reported side effects. Twelve dogs belonged to mixed breeds and of them, two were Chihuahua mixes. The authors summarize that “The compilation shows that there is an overrepresentation of small dog breeds and this has been the case also for reports from earlier years in Sweden. Studies from other countries, like Great Britain and the USA, also show clearly that a low body weight is a predisposing factor for side effects” (Tjälve et al. 2016: 19, my translation from Swedish). Besides belonging to small breeds, most of the dogs being reported for side effects were puppies up to three months old as well as dogs of one years old. There was no variation depending on sex.

From the text above, we can conclude that the immediate side effect can be anaphylactic reactions. As was told, these can be life threatening. Those who are the most vulnerable to these side effects seem to be small dogs. There has been severe criticism against the directive from the vaccine producers, that all dogs, disregarded of size, should have the same dose (e.g. Dodds 2015). Dodds has even done a study to test the efficacy of a vaccine dose reduced to half in a group of 13 adult dogs of a small breed and she showed that the lower dose was sufficient in these dogs (Dodds 2015). In spite of both criticism and research that shows that it can be detrimental to small dogs with the present vaccine doses, the producers do not change their directives and veterinarians have to give the full dose to all dogs, big and small, since they have to follow these directions.

Besides the anaphylactic reactions, vaccinations can also give immunological diseases as well as other health issues, and this is often related to breeds. In an article published already in 2001, W. Jean Dodds write that since this risk exists, “clinicians need to be aware of this potential and offer alternative approaches for preventing infectious diseases in these animals. Such alternatives […] include: measuring serum antibody titers; avoidance of unnecessary vaccines or overvaccination; and using caution in vaccinating ill, geriatric [etc.] individuals, and animals from breeds or families known to be at risk for immunological reactions” (Dodds 2001: 211).  Dodds further writes:

“The clinical signs associated with nonanaphylactic vaccine reactions typically include fever, stiffness, sore joints and abdominal tenderness, susceptibility to infections, neurological disorders and encephalitis, autoimmune hemolytic anemia […] or immune-mediated thrombocytopenia […].” (Dodds 2001: 211)

As seen above, Dodds points out dogs that are immunologically vulnerable as those at risk when vaccinated. The picture given by Dodds regarding the effects upon the immune system can be found also in studies of humans’ reactions to vaccines (e.g. Shoenfeld and Aron-Maor 2000).

In Sweden “all” dogs usually get the vaccine shot Nobivac DHPPi every third year and as was pointed out above this preparation contains four vaccines, against CDV, CAV-1, CPV-2 and parainfluenza. This preparation contains modified live virus (MLV) from the four viruses as well as a phosphate-buffered solution.

We do not have rabies in Sweden and Swedish dogs who never go abroad are not vaccinated against rabies. However, in other continents, like America, Africa and Asia, rabies is prevalent. In the USA, the legislation regarding rabies vaccination differs between states. In some states it is invoked by the law that all dogs shall be vaccinated against rabies every three years, whereas in others not ( In Europe, rabies is prevalent in the Eastern and parts of southern Europe and therefore dogs who travel within the EU must have a valid rabies vaccination.

Here is a map that shows the degree of risk of rabies in different countries:

The vaccination against rabies contains inactivated rabies virus, aluminum phosphate, which is an adjuvant (a substance that is added to help the virus to work better as a vaccine), thimerosal, sodium dihydrogen phosphate, sodium hydrogen phosphate and water for injection fluids. Aluminum is slowly accumulated in the brain, seems to affect the central nervous system and has been related to Alzheimer’s and Parkinsons’s diseases as well as ALS and dialysis dementia (Wilhelmsson 2007: 499). Thimerosal is a preservative and it contains quicksilver. It was used in Swedish vaccines until 1992 (Swedish Public Health Authority about thimerosal in vaccines), and later it was generally removed from human vaccines in the USA and Europe. Quicksilver is strongly neurotoxic and can further damage the immune system, stomach, intestines and the liver. It has been related e.g. to autism, Alzheimer’s disease and dementia (Wilhelmsson 2007: 509ff.).

As is seen above rabies vaccination of dogs can have serious side effects. In a study from 2010 Schultz et al. say that “Two doses of the core rabies vaccines given 3–4 weeks apart are likely to provide many years of immunity in both cats and dogs”, referring to Schultz et al. (1977). There are studies that indicate that a vaccination against rabies gives the dog life-long immunity (Schultz et al. 1977; see also Brown 2017 and Scott (no year mentioned)). In a study from 2006, Schultz et al. show in a table the DOI of rabies vaccination on dogs is three years or more at challenge and seven years or more when serologically tested (Schultz et al. 2006: 77 (my italics)).

Responsible vaccination, what can we demand as dog owners?

I think that the most important thing in the care of our dogs is that we as dog owners are well informed and can do conscious choices. We will never come to exactly the same conclusions but the more we know the more we can take actions to optimize the possibility for our dogs to live a healthy happy life. Below I will list things to think about and do as well as things I wish could be done to diminish the “vaccine load” on our pups.

  • The first thing I would like is that it is made easy accessible for the common dog owner/breeder to test whether puppies have maternally-derived antibody (MDA), i.e. an immune defense that commonly lasts up to the 8 – 12th week of the puppy’s life. If the puppy still has the MDA protection, a vaccination has no effect. I think it would be dog-friendlier to have the MDA defense tested every two weeks than to vaccinate it “just in case”.
  • Vaccinate the puppy when the MDA seems to wane.
  • If the MDA is gone, a vaccine should give the expected effect.
  • Instead of giving a six or twelve months “booster” of vaccines, it should be checked again whether the dog has antibodies against the diseases that it was vaccinated for as a puppy.

The VGG wrote already in their 2010 guidelines that there were commercial test kits to check the antibodies, and that

“These test kits have proven popular with veterinarians who wish to be able to offer their clients an alternative to routine core revaccination at 3-yearly intervals, but the kits remains relatively expensive and unfortunately, at present, testing costs more than a dose of vaccine” (Day et al. 2010: 8).

If the six or twelve month’s old dog has antibodies, it should not be vaccinated and it will probably not need any further core vaccinations in its life. Also the VGG recommends measuring of antibodies instead of routine vaccination:

“The VGG recognizes that at present such serological testing might be relatively expensive. However, the principles of ‘evidence based veterinary medicine’ suggest that testing for antibody status […] should be better practice than simply administering a vaccine booster on the basis that this would be ‘safe and cost less’.” (Day et al. 2016: 10)

  • Aluminum and quicksilver should not be used anymore in pet vaccines. As was pointed out above, quicksilver was removed from human vaccines in Sweden already in 1992, followed by USA and Europe somewhat later. Aluminum is still used in human vaccines as an adjuvant, which is the same use it has in pet vaccines. Although it is a very little amount, it should be replaced with something healthier.
  • The manufacturers of pet vaccines should relate the dose to the weight of the dog. In that way, small dogs would probably not be overrepresented among those with side effects anymore.
  • Precautions should be made if a dog with immunological issues in relatives is to be vaccinated. For these dogs, vaccinations containing aluminum and quicksilver (thimerosal) should be avoided completely.
  • Instead of demanding of dogs in areas where rabies exists that they are vaccinated every three years, it should be easily accessible to measure the antibodies instead and only vaccinate if needed.
  • Several vaccines should not be given in the same shot. Vaccinations are used to imitate real infections in order to activate the immune system. It is not common to get more than one viral disease at a time. It might be that the immune system gets overwhelmed when having to deal with several viruses at one time.
  • If an illness is not lethal and dogs most commonly recover fully from it, it should be considered not to give dogs a vaccination against that illness.

Sources and further reading:

Beck-Friis, Johan. 2006. “Längre vaccinationsintervall rekommenderas av internationella experter”. Svensk veterinärtidning 1, 40–43.

Brown, Jackie. 2017. “The Immunity Challenge: Vaccines and pets”. Veterinary Practice News.

Day, M. J., M. C. Horzinek and R. D. Schultz. 2010. “Guidelines for the vaccination of dogs and cats”. Journal of Small Animal Practice 51, 338–356.

Day, M. J., M. C. Horzinek, R. D. Schultz and R. A: Squires. 2016. “Guidelines for the vaccination of dogs and cats”. Journal of Small Animal Practice 57, 1–45.

Dodds, W. Jean. 2001. “Vaccination Protocols for Dogs Predisposed to Vaccine Reactions”. Journal of the American Animal Hospital Association 37, 211–214. 

Dodds, W. Jean. 2015. “Efficacy of a half-dose canine parvovirus and distemper vaccine in small adult dogs: A pilot study”. AHVMA Journal 41, 11–21.

Dodds, W. Jean. 2017. “Parainfluenza in dogs: what is it?Hemopet.

Schoenfeld, Y. and A. Aron-Maor. 2000. “Vaccination and Autoimmunity – ‘Vaccinosis’: A Dangerous Liaison?”. Journal of Autoimmunity 14, 1–10.

Schultz, R. D. 2006. “Duration of immunity for canine and feline vaccines: A review”. Veterinary Microbiology 117, 75–79.

Schultz, R. D., B. Thiel, E. Mukhtar, P. Sharp and L. J. Larson. 2010. “Age and Long-term Protective Immunity in Dogs and Cats”. Journal of Comparative Pathology, 102–108.

Schultz, R.D., M.J. Appel, L.E. Carmichael. 1977. “Canine vaccines and immunity”. R.W. Kirk (ed.). Current Veterinary Therapy VI. Philadelphia: WB Saunders Co., 1271–1275.

Scott, Dana. “Lifelong Immunity – Why Vets Are Pushing Back”. Dogs Naturally.

Statens veterinärmedicinska anstalt (SVA). “Infektiös hepatit”.

Statens veterinärmedicinska anstalt (SVA). “Parvovirus”.

Statens veterinärmedicinska anstalt (SVA). “Valpsjuka hos hund”.

Sykes, Jane E. 2014. Canine and Feline Infectious Diseases. California: University of California Davis.

Tjälve, Hans, Peter Ekström and Anna-Karin Bengtsson. 2016. “Biverkningar hos hund rapporterade för vacciner, antiparasitära medel och antibiotika”. Svensk veterinärtidning, 18.

Wilhelmsson, Peter. 2007. Näringsmedicinska uppslagsboken.

Windahl, Ulrika and Jessica Ingman. 2009. “Grundvaccination av hund och katt”. Statens veterinärmedicinska anstalt (SVA), 51–54.