Vaccination is a procedure intended to trigger an immune response. Immunization, in turn, means the development of immune protection.<\/p>\n
These concepts are related, but they are not interchangeable. Administering a vaccine does not guarantee the same immune response in every individual animal, and reaching a booster due date does not automatically mean that previously established protection has disappeared.<\/p>\n
Immune protection may last considerably longer than routine revaccination intervals. For example, a country may require a dog to receive a rabies booster every two years, although the manufacturer of the vaccine used has established a three-year duration of immunity. Research, however, has shown that in some dogs actual immune protection may persist for six, seven or even more years.<\/p>\n
This means that a national vaccination requirement, the manufacturer’s established duration of immunity and a dog’s actual immune protection may follow different timelines. Reaching the revaccination deadline does not automatically mean that the dog’s immune protection has disappeared by that point.<\/p>\n
This is more than a theoretical possibility. Studies have documented long-term protection against canine distemper, parvovirus and infectious hepatitis even years after the usual booster due date has passed.<\/p>\n
A vaccine’s officially approved duration of immunity indicates the period for which the manufacturer has submitted the required evidence. It does not necessarily represent the maximum duration of the immune system’s protection.<\/p>\n
Ronald D. Schultz, who lived from 1943 to 2024, was an American veterinary immunologist and professor of veterinary medicine at the University of Wisconsin\u2013Madison. He studied immune responses in animals and the duration of vaccine-induced immunity for more than forty years.<\/p>\n
He began studying canine vaccines back in the 1970s, when annual revaccination was standard practice.<\/p>\n
Schultz did not limit himself to theoretical positions. His research group’s work involved approximately one thousand dogs, and immune protection was assessed both by measuring antibodies and through experiments involving exposure to the pathogen.<\/p>\n
He was also a founding member of the Vaccination Guidelines Group of the World Small Animal Veterinary Association, or WSAVA, and helped develop the organization’s first three global guidelines for vaccinating dogs and cats.<\/p>\n
As early as 1978, Schultz and his colleagues recommended moving away from automatic annual revaccination and considering longer intervals.<\/p>\n
His decades of research helped change our understanding of how long vaccine-induced immune protection can actually persist.<\/p>\n
Research by Schultz and his colleagues has shown that protection against canine distemper, parvovirus and infectious hepatitis can persist considerably longer than routine revaccination intervals.<\/p>\n
Studies have found protection five or more years after vaccination, and even longer protection has been documented for some core vaccines.<\/p>\n
The duration of protection has been assessed both by measuring antibodies and through experiments in which vaccinated animals were subsequently exposed to the pathogen.<\/p>\n
These two research methods do not provide exactly the same information. The presence of antibodies indicates a measurable immune response, whereas protection against disease can be assessed more directly through challenge studies.<\/p>\n
In her discussion, Karen Becker distinguishes core vaccines, such as those against canine distemper, parvovirus and adenovirus, from non-core vaccines, whose need depends more on an animal’s exposure risk. For example, the effects and duration of protection of vaccines against leptospirosis and kennel cough differ from those of core vaccines. We therefore cannot assume the same duration of immune protection for every disease or conclude that the presence of antibodies always means complete protection against infection or shedding the pathogen.<\/p>\n
Becker also discusses sterilizing immunity, in which the immune response prevents an infection from becoming established. It is important, however, to distinguish protection against severe disease, protection against infection and the ability to prevent onward transmission. Long-term immune protection does not automatically mean that every vaccine and every dog will completely prevent infection or transmission.<\/p>\n
The Rabies Challenge Fund studies, in which Schultz participated, investigated how long protection against rabies could persist after vaccination.<\/p>\n
According to the published results, four out of five dogs were protected after six years and seven months. After seven years and one month, six out of twelve were protected, and after eight years, one out of five.<\/p>\n
These results do not mean that rabies protection lasts seven or eight years in every dog. The study groups were small, and protection did not persist equally in all animals. Nevertheless, the challenge experiments directly demonstrated that in some dogs protection can persist considerably longer than the usual three-year revaccination interval.<\/p>\n
We therefore need to distinguish three things: the duration of immunity established by the vaccine manufacturer, the national revaccination deadline and an individual dog’s actual immune protection.<\/p>\n
In 2017, integrative veterinarian Judy Morgan described a case in which a client’s dog was vaccinated against rabies every year, although the applicable requirements allowed a vaccine with a three-year duration of immunity.<\/p>\n
When the owner asked why the dog needed another vaccine every year, the clinic initially cited the dog’s therapy-dog status, then state and local government requirements. Morgan checked these explanations and found that none required annual vaccination.<\/p>\n
Morgan also contacted the vaccine manufacturer. According to her account of that conversation, there was no medical justification for vaccinating the dog annually, and a product with a three-year duration of immunity was also appropriate.<\/p>\n
This case raises an important question: is the decision to revaccinate always based on an animal’s actual needs, or can established practices also influence it?<\/p>\n
Morgan points out that the date of vaccination and the duration of immune protection are not the same thing. Her discussion centers on whether the animal already has adequate protection and whether another vaccine will provide additional benefit.<\/p>\n
At the same time, one client’s story does not show how frequently similar situations occur in veterinary practice. It illustrates why the reasons behind a vaccination decision should be verifiable.<\/p>\n
The immune system’s ability to protect the body does not depend solely on how many antibodies can be measured in a blood sample at a particular moment. Immune memory cells also play an important role: they may enable the body to respond rapidly when it encounters the pathogen again.<\/p>\n
A titer test measures antibody levels. For certain canine core vaccines, a positive result provides important information about protection. A low or negative result does not, however, always mean that all immune memory has disappeared.<\/p>\n
Rabies is a special case because the disease is almost always fatal once clinical signs develop. We therefore cannot conclude that a dog is definitely protected simply by assuming that immune memory is present.<\/p>\n
A titer test result must also be interpreted according to the purpose for which the test is being used.<\/p>\n
Integrative veterinarian Karen Becker has discussed the difference between immunization and vaccination in light of Ronald Schultz’s research. She emphasizes that the aim of vaccination is not to administer as many vaccine doses as possible, but to establish effective immune protection.<\/p>\n
Becker has described a titer test performed on her dog Homer, which showed a measurable protective antibody response. On that basis, she did not consider additional core vaccines necessary for him.<\/p>\n
Another important question in her discussion is whether every subsequent booster is always necessary after correctly timed, successful primary vaccination. Becker draws on Schultz’s work, which shows that immune protection from some core vaccines can be very long-lasting.<\/p>\n
Becker recommends using titer tests to assess whether a dog has developed a measurable immune response and whether it persists. Her position does not, however, mean that one vaccine dose produces lifelong protection in every dog. In puppies in particular, the response to vaccination depends on when maternally derived antibodies have declined sufficiently.<\/p>\n
An animal’s actual exposure risk also depends on its lifestyle. Becker recommends considering where the animal lives, which other animals it encounters and which infections it is likely to be exposed to when making vaccination decisions. For example, the risks faced by an indoor-only cat and a cat that spends a lot of time outdoors are not always the same. This does not mean that an indoor animal has no infection risk at all: the specific disease and its routes of transmission need to be assessed.<\/p>\n
In Becker’s approach, five questions deserve consideration before a vaccination decision:<\/p>\n
These questions support an individual discussion; they are not a universal list of situations in which vaccination is always contraindicated.<\/p>\n
Veterinary immunologist W. Jean Dodds has also devoted considerable attention to titer testing and individualized vaccination.<\/p>\n
In her approach, administering a vaccine must be distinguished from the immune response that follows. A titer test can assess whether measurable antibodies against a particular pathogen are present in the blood.<\/p>\n
For canine distemper, parvovirus and adenovirus, a positive antibody result can be important evidence of protection. A titer test can therefore help determine whether revaccination is necessary or whether the dog already has measurable immune protection.<\/p>\n
Dodds also discusses the importance of immune memory. Antibody levels can decline over time without all previously established immune memory necessarily disappearing.<\/p>\n
However, titer tests cannot be interpreted in the same way for every infectious disease. The relationship between antibodies and actual protection is well studied for some diseases, but not for others.<\/p>\n
The WSAVA vaccination guidelines also discuss antibody testing for canine core vaccines. The use of titer tests is therefore not confined to integrative veterinary medicine.<\/p>\n
Puppies receive antibodies from their mother, which protect them during their first weeks of life. Most of this protection is obtained through colostrum after birth.<\/p>\n
Those same antibodies can, however, interfere with the development of an adequate immune response to a vaccine.<\/p>\n
The amount of maternally derived antibodies and the rate at which they decline vary between puppies. Age alone therefore cannot establish that all puppies are equally protected or equally able to respond to vaccination at a particular point.<\/p>\n
This is why the WSAVA guidelines recommend a series of core vaccinations for puppies, with the final dose usually given at sixteen weeks of age or older. A later dose may also be justified in high-risk situations.<\/p>\n
Integrative veterinarian Peter Dobias has criticized very early puppy vaccination and emphasized the importance of maternally derived antibodies.<\/p>\n
According to his discussion, puppies aged six to eight weeks may still have maternally derived antibodies in their blood. These can bind to vaccine antigens and prevent the puppy from developing an adequate immune response of its own.<\/p>\n
Dobias takes his explanation further. He argues that vaccinating too early can reduce the puppy’s existing maternal protection without the vaccine simultaneously producing sufficient new protection. In his view, this can leave the puppy susceptible to infection.<\/p>\n
This is an important question, but two issues must be distinguished. The ability of maternal antibodies to interfere with a vaccine response is well documented. The claim that vaccination itself removes maternal protection and thereby leaves the puppy unprotected requires separate evidence. A later negative titer test alone does not establish that mechanism.<\/p>\n
Dobias has described his dog Pax’s puppyhood and his decision to use antibody measurements to time vaccination.<\/p>\n
He says he asked the breeder not to vaccinate Pax at six weeks, although the other puppies in the same litter received a vaccine then. At twelve weeks, Dobias had Pax’s antibodies against distemper and parvovirus measured. The results were positive for both diseases. Dobias interpreted these results as a sign that maternally derived antibodies were still present in Pax’s blood and planned to repeat the measurements later.<\/p>\n
Pax’s example illustrates why timing puppy vaccination is not always as simple as choosing one fixed age. One eight-week-old puppy may still have substantial maternal protection, while in another puppy of the same age it may already have declined considerably.<\/p>\n
One positive titer test does not, however, always establish whether the antibodies came from the mother or from the puppy’s own immune response. Making that distinction requires consideration of vaccination history, age and, where necessary, repeat measurements.<\/p>\n
Dobias has also described monitoring antibodies in his previous dog, Skai. These cases illustrate his individual approach, but results from individual dogs cannot automatically be generalized to all puppies.<\/p>\n
Karen Becker has also discussed the use of a vaccination nomograph.<\/p>\n
The purpose of a nomograph is to estimate, from the mother’s antibody levels, when maternally derived antibodies in the puppies may decline to a level at which vaccination is more likely to succeed.<\/p>\n
This is an interesting way to plan vaccination timing more precisely, but an estimate based on the mother’s antibodies does not entirely replace assessment of the puppy’s individual immune response.<\/p>\n
Here, the approaches of Dobias, Becker and conventional veterinary immunology converge on an important point: maternal antibodies can affect the outcome of vaccination, and puppies do not all develop immune protection on the same schedule.<\/p>\n
The differences lie mainly in how that knowledge is applied in practice.<\/p>\n
A dog’s health must be considered when deciding on vaccination. Vaccine product information commonly requires that only clinically healthy animals be vaccinated.<\/p>\n
Dogs with chronic diseases, active inflammation or previous vaccine reactions need particular attention. Integrative veterinarian Judy Morgan emphasizes individual assessment and is especially cautious with dogs that have previously developed a reaction after vaccination.<\/p>\n
I have also contacted Estonia’s Agriculture and Food Board (PTA) myself with a concern about a health risk associated with vaccinating a dog. My enquiry did not even reach the point where the possibility of an individual medical exemption was substantively considered.<\/p>\n
Years earlier, I also contacted the Ministry of Rural Affairs about my very sensitive dog. The response at the time was that the established vaccination guidelines had to be followed. That earlier correspondence and my later contact with the PTA illustrate why I believe the possibility of medically justified exemptions needs official, substantive consideration.<\/p>\n
This experience raises the question of what options an owner has when mandatory vaccination may harm an individual animal’s health.<\/p>\n
We discuss this topic in more detail in a separate article, \u201cWhy is vaccinating a sick animal dangerous?\u201d.<\/p>\n
In Estonia, dogs must be revaccinated against rabies according to the vaccine leaflet, but no less frequently than every twenty-four months. At the same time, vaccines are in use for which the manufacturer has established a three-year duration of immunity.<\/p>\n
For example, a three-year duration of immunity for the rabies component of the Bioveta Biocan NOVEL range was documented years before the current discussion.<\/p>\n
Other European countries use different approaches. In the Czech Republic, revaccination is linked to the vaccine’s approved period of validity. Belgium ended the general requirement for rabies vaccination of domestic pets in 2016, while retaining separate requirements for international movement.<\/p>\n
These examples do not mean that the countries’ epidemiological circumstances are identical. They do show, however, that different legal approaches to rabies prevention are possible.<\/p>\n
In Estonia, the possibility of individual exemptions for dogs with health problems was raised in official correspondence as early as 2021. In 2022, the Ministry of Rural Affairs confirmed that exemptions based on a veterinarian’s assessment and antibody titer testing could be considered in the future.<\/p>\n
This question deserves a clear, up-to-date answer.<\/p>\n
The date in a vaccination record indicates when vaccination must be repeated under the applicable requirements. It is not a direct measurement of the day on which an individual dog’s immune protection ends.<\/p>\n
Likewise, the existence of long-lasting immune memory does not automatically mean that every dog is protected for life.<\/p>\n
The duration of immune protection depends on the pathogen, the vaccine, previous vaccinations and the animal’s individual immune response.<\/p>\n
Ronald Schultz’s research has helped demonstrate how long immune protection can persist. Judy Morgan’s client story raises the issue of unjustifiably frequent revaccination. Karen Becker, Jean Dodds and Peter Dobias emphasize, from different perspectives, the importance of individual immune responses, antibody testing and vaccination timing.<\/p>\n
The message their approaches share is that administering a vaccine does not, by itself, fully answer whether an animal has been immunized or how long its protection will last.<\/p>\n
Vaccination decisions therefore need to distinguish scientifically measured protection, the manufacturer’s established duration of immunity and national requirements.<\/p>\n
These are related, but they are not the same thing.<\/p>\n