Over-Vaccination in Dogs & the Role of Titre Testing
Vaccination is one of the most important preventive healthcare measures in dogs. Core vaccines protect against life-threatening diseases such as canine parvovirus, canine distemper virus and canine adenovirus. These diseases can cause severe illness and death, particularly in puppies and unvaccinated animals.
However, in recent decades veterinary medicine has moved away from routine annual vaccination toward a more individualised approach. Scientific evidence has shown that immunity from many core vaccines lasts for several years, meaning that yearly revaccination may not always be necessary (Schultz, 2006).
For breeds such as the Cavalier King Charles Spaniel, which are known to have several inherited health vulnerabilities, minimising unnecessary medical interventions is particularly important. One strategy that is increasingly used to help avoid unnecessary vaccination is antibody titre testing. This article explains the issue of over-vaccination, potential risks associated with unnecessary vaccines, and how titre testing can assist in developing a more evidence-based vaccination strategy.
Vaccination & Duration of Immunity
Vaccines work by stimulating the immune system to produce antibodies and immune memory against specific pathogens. Once this immune memory is established, the body can respond rapidly if exposed to the disease in the future.
Research has demonstrated that immunity following vaccination against the major canine core diseases—canine distemper virus (CDV), canine parvovirus (CPV-2) and canine adenovirus (CAV-2)—lasts at least three years and often longer after the initial vaccination series and booster (Schultz, 2006).
Modern veterinary guidelines therefore recommend that these core vaccines are generally administered at three-year intervals rather than annually, provided the dog has completed its puppy series and first adult booster (AAHA; WindanSea Veterinary Clinic).
Despite these updated recommendations, some dogs may still receive vaccinations more frequently than necessary. This practice is commonly referred to as over-vaccination.
What Is Over-Vaccination?
Over-vaccination occurs when vaccines are administered more often than required to maintain protective immunity. It does not mean vaccination itself is harmful; vaccines remain an essential component of preventive veterinary care. Instead, the concern relates to giving repeat vaccines when a dog already has adequate immunity.
Because the immune system retains memory after vaccination, additional doses may provide little or no additional protective benefit if the animal is already immune. In such cases, repeated vaccination primarily results in additional immune stimulation rather than improved protection.
Potential Negative Effects of Over-Vaccination
Vaccines are generally safe, and serious reactions are uncommon. However, adverse events can occur and are one reason veterinarians aim to vaccinate only as frequently as necessary.
Short-Term Vaccine Reactions
The most common adverse events associated with vaccination are mild and transient. These include:
Fever
Lethargy
Swelling or soreness at the injection site
Allergic reactions
These reactions are recognised in veterinary medicine and usually resolve within a short period (Hogenesch, 1999).
Large population studies estimate adverse reactions occur in approximately 19.4 cases per 10,000 vaccinations, indicating that while vaccines are generally safe, reactions do occur in a small percentage of dogs (Morris Animal Foundation).
Immune-Mediated Disease
More serious reactions are rare but have been reported. In some cases vaccination has been associated with immune-mediated conditions, where the immune system mistakenly attacks the body’s own tissues. These conditions include immune-mediated haemolytic anaemia (IMHA) and other autoimmune disorders (Hogenesch, 1999).
Although the causal relationship between vaccination and autoimmune disease is still being studied and appears uncommon, the possibility reinforces the importance of avoiding unnecessary immune stimulation.
Increased Risk in Small Dogs
Research has shown that smaller dogs and dogs receiving multiple injections at one visit may have a higher risk of reported vaccine adverse events (Moore et al., 2023).
This is particularly relevant for toy breeds such as the Cavalier King Charles Spaniel, which typically weigh between 5–8 kg.
Why This Matters for Cavalier King Charles Spaniels
Cavalier King Charles Spaniels are beloved companion dogs but unfortunately have a high prevalence of inherited health conditions. The most significant include:
Mitral valve disease (MVD)
Syringomyelia
Chiari-like malformation
Certain immune-mediated conditions
Because many Cavaliers already have underlying health vulnerabilities, responsible healthcare management focuses on minimising unnecessary stress on the immune system and body wherever possible.
This does not mean avoiding vaccination entirely. Rather, it means ensuring vaccines are administered only when they are actually required to maintain protection.
What Is Titre Testing?
Antibody titre testing is a diagnostic blood test used to measure the level of protective antibodies in a dog’s bloodstream.
Specifically, titre tests measure antibodies against the core canine diseases:
Canine parvovirus (CPV)
Canine distemper virus (CDV)
Canine adenovirus (CAV)
These antibodies indicate whether the dog’s immune system still recognises and can defend against these pathogens.
If the antibody level is above a recognised protective threshold, the dog is considered immune and revaccination is generally unnecessary at that time.
How Titre Testing Helps Prevent Over-Vaccination
Titre testing allows veterinarians to make vaccination decisions based on objective evidence of immunity rather than a fixed schedule.
The process is straightforward:
A small blood sample is collected from the dog.
The sample is analysed in a laboratory or using an in-clinic test.
The antibody levels are measured and compared with known protective thresholds.
If antibody levels are high or protective, the dog does not need another vaccine. If levels are low or absent, a booster vaccination may be recommended (DVM360; Merrillville Veterinary Clinic).
Studies have shown that many adult dogs maintain protective antibody levels for years following vaccination. For example, one study found that 86% of dogs retained protective antibodies against parvovirus, even after prior vaccination schedules (Taguchi et al., 2011).
By identifying dogs that remain protected, titre testing can help prevent unnecessary booster vaccinations.
Limitations of Titre Testing
While titre testing is a valuable tool, it is important to recognise its limitations.
It primarily assesses immunity for core viral vaccines (distemper, parvovirus, adenovirus).
It does not reliably measure protection against some non-core diseases, such as leptospirosis or kennel cough.
A negative or low titre result does not necessarily mean the dog has no immune memory, but it generally indicates a booster vaccine may be beneficial.
Therefore, titre testing is best used as part of an individualised vaccination plan developed with a veterinarian.
Vaccination remains a cornerstone of responsible dog ownership and disease prevention. However, modern veterinary research has demonstrated that immunity from core canine vaccines often lasts several years. As a result, routine annual vaccination is no longer considered necessary in many cases.
Over-vaccination refers to administering vaccines more frequently than required to maintain protection. While vaccines are generally safe, unnecessary revaccination may increase the likelihood of adverse reactions and immune stimulation.
For Cavalier King Charles Spaniels, a breed already predisposed to several health issues, careful management of preventive healthcare is especially important.
Titre testing provides a practical solution by allowing veterinarians to measure existing immunity and determine whether vaccination is actually required. By using titre testing alongside regular veterinary health checks, owners can ensure their Cavaliers remain protected from infectious disease while avoiding unnecessary medical intervention.
References
Hogenesch, H. (1999). Vaccine-induced autoimmunity in the dog. Advances in Veterinary Medicine. Moore, G. E., et al. (2023). Breed, smaller weight, and multiple injections are associated with increased adverse event reports following canine vaccination. Journal of the American Veterinary Medical Association. Morris Animal Foundation. (n.d.). The science behind pet vaccines: Safety, risks, and benefits. Schultz, R. D. (2006). Duration of immunity for canine and feline vaccines: A review. Veterinary Microbiology. Taguchi, M., et al. (2011). Antibody titers for canine parvovirus, distemper virus and adenovirus in vaccinated dogs. Journal of Veterinary Medical Science. WindanSea Veterinary Clinic. (2020). Fact vs rumor: The dramatic change in pet vaccination. American Animal Hospital Association. (2022). Canine vaccination guidelines. DVM360. (2024). Understanding the use of antibody titers in veterinary practice. Gonzalez, S. E., et al. (2023). Influence of age and vaccination interval on canine core vaccine titers. Veterinary Immunology. Inner South Veterinary Centre. (2018). Titre testing in dogs. Merrillville Veterinary Clinic. (2025). Titers, nomographs, and smarter pet vaccination.