Be forewarned, this is a long entry, but I want you to have sufficient information to be an informed partner in decision making with your vet about what is best for your dog. While I hope you will take the time to read this so you understand the current recommendations, I have provided a summary at the end of this post. Spoiler alert: I have been getting titers rather than repeated core vaccines for my goldens for more than 20 years, which is as long as I’ve been able to find veterinarians who were willing to do that. I was living in Wisconsin early in this time frame and, with one of the best veterinary immunologists in the country not too far away, I may have had earlier access than many to titer testing as an option. Still, I had to make a lot of calls to find a vet who shared my viewpoint. OK, now I’ve given away the ending to some extent, but there are many angles to this topic, so please keep reading. Health care decisions about your dog need to be based on informed discussions, not quick sound bites that came from the internet.
How immunity and vaccines work. Let’s start with a very simplistic overview of how vaccines work (my immunologist colleagues will cringe, but they’ll get over it). Vaccines are created with actual disease-causing bacteria or viruses that have been altered so that they do not cause the disease with which they are associated. Vaccines come in a variety of forms; you may have heard the terms “killed virus,” or “modified live virus,” both of which describe the way a disease-causing organism in a vaccine is altered so it does not make your dog ill. When a vaccination is given, one of the things that happens is the lymphatic system produces antibodies to fight off the invading organism in the vaccine. The antibodies remain in the body for a time, sometimes a very long time, and are primed to attack that virus or bacterium should it be encountered in the future. There are a number of complex and interacting mechanisms that are involved in the immune response and different types of immunity, but antibodies generally are the first line of defense and the one involved with the titer testing we will be discussing. So I’ll leave it at that.
Sometimes more than one injection of the vaccine is needed to generate sufficient antibody response. This is the case with “puppy shots” and also the reason that follow-up or “booster” injections sometimes are recommended after the initial injections. Some animals do not respond completely to the vaccine and develop weak or limited immunity, though this is uncommon.
How long is my dog immune after a vaccination? For many vaccines, immunity may develop that can last for several years or, in many cases, much longer. The type of original vaccine as well as the animal’s response will affect the duration of immunity (DOI). For some, it may last only about one year, which is why the Bordetella vaccine and a few others are recommended for annual revaccination.
Dr. Ronald Schulz of the University of Wisconsin (Madison) School of Veterinary Medicine, one of the leading researchers in the area of veterinary vaccines and an author on the recent guidelines created by the American Animal Hospital Association (AAHA) and the World Small Animal Veterinary Association (WSAVA), has done extensive research on the duration of immunity achieved with initial core vaccines. His research, going as far back as the 1970s and using the best techniques for studies of this type, has demonstrated repeatedly that the core vaccines provide immunity on average for 7 years or longer and, in some cases, immunity from initial vaccination may last for the life of the dog.
Core vaccines are the ones considered to be critical to the health of the dog and are recommended for all dogs. They include only the following at present:
- Modified Live Virus (MLV) or recombinant Canine Distemper
- MLV Parvovirus
- MLV Adenovirus-2
- MLV Parainfluenza Virus
Adenovirus is related to canine hepatitis, so you may know the combination vaccine as the DAPP or DHPP (distemper, hepatitis, parvovirus, and parainfluenza). All other vaccines are considered Noncore, or to be given only if individual circumstances warrant based on a balanced consideration of risk and benefit. Risk includes how likely the dog is to encounter the disease organism based on environment or behavior, the risk to the dog if it contracts the disease, and whether the protective effects of the vaccine warrant the risk of the vaccine administration. Risk assessment might also include whether the disease can be avoided in other ways, for example, through minimizing exposure or using other means of prevention.
In 2003, with evidence increasingly showing that the prevailing standard for yearly re-vaccination was not necessary, the major veterinary and animal hospital associations revised their guidelines to recommend a 3 year interval for re-vaccination. The 3-year interval was a compromise position based on a number of considerations, not based on evidence that immune status lasted only 3 years. Since that time, the recommendation has evolved so that the guidelines now read that the interval between vaccination administrations should be a minimum of 3 years, in other words, as a general principle, a dog should not be vaccinated with core vaccines any more often than every three years. As stated in the current guidelines of the World Small Animal Veterinary Association, “above all, it must be remembered that even a 3-year license is a minimum DOI [duration of immunity] for core vaccines and for most core vaccines the true DOI is likely to be considerably longer, if not lifelong, for the majority of vaccine recipients.”
What to do when your dog is “due” for vaccination (after initial vaccination series is complete)? Immunity does not fall off precipitously on the vaccination “due” date. In addition, there is all that evidence that shows that for many vaccinations immunity lasts much longer than three years, often for the life of the dog. That leaves us with several options: assume the dog continues to have satisfactory immunity and do not obtain additional vaccinations (might be ok, but we have no way of knowing so there is risk to your dog with this option), booster the vaccinations just to be sure (might ensure immunity but there are risks to your dog of unnecessary vaccinations), or do serum titers that provide a measure of current immunity (evidence supports this as best practice). Re-vaccination, if not needed, is of no benefit to the dog; a dog with sufficient immunity does not become more immune, so it is at minimum a waste of money and may be harmful because of possible negative effects of vaccination. An adverse response to vaccine can occur with an array of symptoms and severity that ranges from mild to life threatening. While this is relatively uncommon, it does occur. Animals that are immunocompromised or have other health problems may be more likely to experience adverse reactions and this response also is more common in certain breeds and smaller dogs. There is some evidence that the risk of adverse effects might increase with repeated vaccinations. Vaccines trigger a complex immune response and the outcome of this repeated triggering of the immune system may have detrimental health effects ranging from short term lethargy to serious autoimmune disorders. There is a need for more research in this area although both research and anecdotal reports show that there is at minimum some risk associated with vaccines.
The titer option. Fortunately, we do not have to rely on guess work or just hoping for the best to protect our dogs. Research has shown repeatedly that antibody titers are a good measure of immune status following the initial core vaccination series. (Initial titers sometimes are done after that series to ensure that the dog responded appropriately to the vaccines as there are a small number of dogs who are “non-responders”). The AAHA guidelines note that “a ‘positive’ antibody test result [for the core vaccines] generally does correlate well with protective (sterile) immunity in dogs. This applies to not only laboratory-based testing procedures (quantitative testing) but to in-clinic point-of-care (qualitative testing) antibody kits as well." One deterrent to titer testing had been the fact that it was more expensive, especially with samples sent to a laboratory for testing. As more people have sought titer testing in lieu of repeated vaccinations, and more veterinarians are receptive to this approach, prices have come down and new options are available, including the tests that veterinarians can perform in their own clinics.
The WSAVA guidelines describe titer testing as the better practice compared to repeat vaccination: “The [Vaccination Guidelines Group] 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 (for either puppies or adult dogs) should be better practice than simply administering a vaccine booster on the basis that this would be ‘safe and cost less’.” Titers currently are available for all of the core vaccines. Titers should be monitored regularly to determine when revaccination might be indicated. Most people who use titers to monitor immune status repeat these with the yearly exam. The best interval can be determined by your veterinarian in discussion with you about your dog’s lifestyle and it also will vary depending on the specific vaccine administered previously to your dog.
The rabies vaccination exception. Unfortunately, we are faced with one exception to this decision making process due to the legal requirement for rabies vaccination. Rabies titers are available but few, if any, localities have changed their laws to match best practice for rabies vaccination. Some local governments have a process to apply for an exception with exceptions being considered if the dig is debilitated or otherwise compromised such that the vaccination is likely to be harmful to the dog. These exceptions require approval by a local health officer and may be difficult to obtain. Rules vary by locality. In the event of a bite incident, the dog who is not up to date with rabies vaccination, even if only a few days past the due date, could face dire consequences, a risk that is greater than the risk of contracting rabies if the vaccination becomes past due. So the rabies vaccine is needed when local laws dictate to protect the dog from legal ramifications if not the disease itself. At least the rabies vaccination schedule has been changed to a 3 year interval, and the particular vaccine is of less burden on the immune system than some other vaccine types. Further effort to extend that timeline or to gain acceptance for rabies titers will help alleviate this burden on our dogs.
Summary – Current best practice
The current best practices regarding vaccines and your dog, supported by decades of quality evidence and as expressed in the guidelines of the American Animal Hospital Association and the World Small Animal Veterinary Association, support the following:
1. Ensure baseline immunity through proper administration of core vaccine initial series. For puppies, this involves administration, on the proper schedule, of the recommended “puppy shots” and booster. For adult dogs with unknown vaccine history, there are a couple of different options depending on what is known and the veterinarian’s approach.
2. If finances allow, conduct a titer test to determine responsiveness to the initial vaccines. A blood sample taken about 4 weeks after the last vaccines in the series can be analyzed to determine that the dog is showing the desired immune response. The incidence of non-responders is quite low, so this is not essential, but if you want to be really certain that immunity has been established, this option is available. This may be particularly useful if the plan is to do titers in the future.
3. Avoid unnecessary vaccinations, including re-vaccination and non-core vaccines that are not indicated by your dog's individual situation. Consider carefully with regard to the dog’s lifestyle and risk whether any of the noncore vaccines are needed. Balance the benefits of protection against the risk of the disease, both in terms of the risk of your dog contracting the disease and also the seriousness of the disease if your dog becomes ill.
4. Perform serologic (titer) testing at intervals to determine maintenance of immunity. Revaccinate only when titers indicate booster is necessary (generally before it falls into the negative range) or if changes in the dog’s risk status warrant.
5. If titers are not an option, then minimize vaccination by at least having your dog vaccinated no more frequently than necessary and with only the vaccines appropriate for your dog. Discuss with your vet the best management approach for your dog based on the dog’s lifestyle.
Wishing you and your dog the best of health!
Links for more reading are provided below. I welcome your questions and comments.