Western Veterinary Conference 2008
Ronald D. Schultz, DVM, MS, PhD, Hon. ACVM
Professor and Chair, Department of Pathobiological Sciences,
School of Veterinary Medicine, University of Wisconsin-Madison.
Madison, WI, USA
What Every Veterinarian Needs to Know About Canine Vaccines and Vaccination Programs I & II (2008)
Objectives of the Presentation
Provide essential information on canine vaccines and vaccination programs
General Key Points
1.) Vaccines that should be given to all dogs (core vaccines)
2.) When core vaccines should be given
3.) Optional vaccines for dogs
4.) How to determine if a dog needs an optional vaccine
5.) How often vaccines should be given
6.) Frequently asked questions about vaccines
Overview of the Issue
For many veterinary practitioners canine vaccination programs have been “practice management tools” rather than medical procedures. Thus, it is not surprising that attempts to change the vaccines and vaccination programs based on scientific information have created great controversy and unique methods of resistance to the proposed changes have been and are being developed by certain individuals that resist change. For some practitioners the issues are not duration of immunity for the vaccines, nor which vaccines are needed for the pet, instead it is felt that every licensed vaccine should be given to every pet on an annual or more often basis. Ironically this is fostered by the fact that multivalent products with 9 or more vaccine components can be purchased for the same price or less than a product with one or two vaccine components. A “more is better” philosophy often prevails with regard to pet vaccines. On many occasions practitioners say that “I know many of the vaccines I administer probably aren’t needed but it won’t hurt to give them and who knows the animal may need them some time during their life because of unknown risk.” I have also been told by many practitioners that “I believe the duration of immunity for some vaccines like distemper, parvovirus and hepatitis is many years, but until I find another way to get the client into my office on a regular basis I’m going to keep recommending vaccines annually.” Annual vaccination has been and remains the single most important reason why most pet owners bring their pets for an annual or more often “wellness visit.” The importance of these visits for the health of the pet is exceptional. Therefore, dog owners must understand that vaccines are not the only reason why their dog needs an annual wellness visit. In fact, they must be educated that certain vaccines need not be given at all or that they need not be given very often, whereas other vaccines may need to be given more often than annually. Another reason for the reluctance to change current vaccination programs is many practitioners really don’t understand the basic principles of vaccinal immunity.
A significant number of practitioners believe:
1. The annual revaccination recommendation on the vaccine label is evidence the product provides immunity for (only) one year. Not True. It may not even provide a year’s immunity–or it may provide a lifetime of immunity.
2. That they are legally required to vaccinate annually and if they don’t they will not be covered by AVMA liability insurance if the animal develops a vaccine preventable disease. Not True. They may also be concerned that certain companies will not provide assistance if practitioners don’t vaccinate annually with core vaccines. Not True. In fact most of the companies have now demonstrated their core products provide at least 3 years of immunity and some give a written guarantee.
3. That not revaccinating will cause the animal to become susceptible soon (days or a few weeks) after one year. Not True.
4. If the animal is not revaccinated at or before one year the “whole vaccination program needs to be started again”. Not True.
5. If they don’t continue to revaccinate annually, diseases like canine distemper, canine parvovirus and infectious canine hepatitis (CAV-1) will “reappear and cause widespread disease similar to what was seen prior to the development of vaccines for these diseases.” Not True. The diseases will only reappear if there is no vaccination.
6. That if the revaccination “doesn’t help, it won’t hurt.” Not True.
7. That giving a vaccine annually that has a duration of immunity of 3 or more years provides much better immunity than if the product is given only once during the three years.–Not True. In fact, there are regional/state rabies programs that suggest annual rabies vaccination programs provide better protection than revaccination once every three years regardless of whether a 1 year or 3 year rabies product is used. Not True.
8. That parvovirus vaccines only provide six months of immunity, thus they must give them semi-annually and the CPV-2 vaccines need to be given with coronavirus vaccine to prevent enteritis. Not True. CPV-2 vaccines provide a minimum of 7 years duration of immunity and coronavirus vaccines are not recommended.
9. ”It’s much cheaper to revaccinate the pet annually than it is to treat the disease the animal will develop because it didn’t get revaccinated annually.” The “better safe than sorry” philosophy–it is less expensive to prevent disease than treat it. However, if the core vaccines are given as a puppy and again at a year of age, then annual revaccination is not needed! Furthermore, if a vaccine is given that is not needed and it causes an adverse reaction that is unacceptable and can be very expensive.
10. They feel a need to revaccinate all new dogs/cats coming to their clinic irrespective of vaccination history even when vaccination records are available from another clinic. Presumably the “other clinic” used the wrong vaccine or didn’t know how to vaccinate. Not True.
11. ”Dogs need to be revaccinated annually up to 5 to 7 years of age, then and only then would vaccination every three years be okay.” Not True.
12. ”Surgical procedures, including anesthesia, are immunosuppressive thus dogs should be vaccinated prior to or shortly after surgery.” Not True.
13. ”Because boarding kennels require annual or more often (kennel cough every 6 to 9 months) revaccination, and some require annual revaccination with the core products, practitioners must continue vaccinating annually with all vaccines.” Not True. Help change the kennel rules through education and only use the vaccines that need to be given (e.g., Kennel Cough) annually, not the ones (core) that give long term immunity.
Note: There are kennels that require every licensed vaccine and the vaccines must have been given within 1 year or less prior to admission–help change these rules! Those kennels that are members of the American Kennel Association follow the AAHA Guidelines, but many kennels do not belong to this association.
It will be necessary to correct many of these and additional misunderstandings by providing education to veterinary practitioners, kennel owners and pet owners before significant changes in vaccination programs can or will occur to reduce the over-vaccination of both cats and dogs. However it is equally important that we don’t, in our efforts to prevent over-vaccination, fail to vaccinate often enough, fail to vaccinate all or as many pups with the core vaccines as possible at least once after 16 weeks of age, fail to use products that are necessary, or use products that shouldn’t be used because they don’t provide protection.
I believe every practitioner, kennel owner and dog owner should know the following general information about canine vaccines and vaccination programs:
What vaccines are needed for all puppies?
I do mean all pups, as we only vaccinate approximately 50% of dogs. If we could increase this percentage to 75%, we would be able to eliminate many of the diseases prevented by core vaccines. The “core vaccines,” those that every pup should receive and identified as core by most canine vaccine experts and the AAHA Canine Task Force, include: 1) Canine Parvovirus type 2 (CPV-2), 2) Canine Distemper virus (CDV), 3) Canine Adenovirus type 2 (CAV-2), 4) Rabies Virus (RV).
When do the core vaccines need to be given?
As a minimum, puppies should be given at least one dose at 16 weeks of age or older. Preferably, they should be given three or more times starting at 6 to 9 weeks (I prefer 8 or 9), then at intervals of 2 to 4 weeks. For example, vaccinate at 9, 12, and 15 weeks. It is critical that the last dose be given at 14 to 16 or more weeks of age, regardless of number of doses given earlier. It is also important not to give vaccines earlier than 5 to 6 weeks unless there is a significant risk of a specific disease, then give only the vaccine for the disease you want to prevent (e.g., CPV-2). Never vaccinate a pup less than 4 weeks of age, because the modified live vaccines are not designed for these very young animals. The most effective canine core products currently will include modified live and recombinant vaccines alone or in combination. The combination products with CPV-2, CDV and CAV-2 currently often include canine parainfluenza (CPI) virus. New “core only” products have been and are being developed that don’t have CPI, however, the CPI will not cause a problem if and when used as a parenteral 5 way combination product. However, the most effective route to vaccinate for CPI is intranasal, as local immunity is more important than systemic immunity.
After the puppy vaccination series is completed, revaccination is recommended by AAHA Canine Guidelines again at one year of age or one year after the last puppy vaccination. Rabies must be given again at 1 year, then every 3 years, whereas, the other core vaccines need not be given again after the one year dose for at least 3 or more years. There is no benefit from annual rabies vaccination and most one year rabies products are similar or identical to the 3-year products with regard to duration of immunity and effectiveness. However, if they are 1 year rabies vaccines, they must be legally given annually! Rabies vaccine is the only canine vaccine requiring a minimum duration of immunity study and labeled as 1 year or 3 year by the USDA. However, revaccination annually does not necessarily improve immunity. Annual revaccination does significantly increase the risk for an adverse reaction in the dog. I would recommend, if you really want to be sure the puppy vaccination program was successful, that a CDV and CPV-2 antibody test be performed 2 or more weeks after the last puppy vaccination. Laboratory tests as well as “in-office test” for CDV and CPV-2 are available. If there is no antibody, revaccinate and perform a test two or more weeks after revaccination. If you still don’t have antibody, change the product and revaccinate. Antibody tests (titers) are very useful at these times to ensure the animal is immunized. The problem with antibody tests is they are often very expensive, thus in general, these tests won’t be used. As an alternative to revaccinating at one year for CDV, CPV-2 and CAV-2, you could revaccinate at 6 months to ensure the animal has responded to the last dose in the puppy series rather than waiting until 1 year, as recommended in the AAHA Guidelines. Revaccinate not more often than every 3 years. The minimum duration of immunity for the core vaccines except rabies is at least 5 to 7 years based on challenge and/or antibody titers (Table 1). Thus revaccinating annually will not improve protection. Ironically “the better safe than sorry philosophy” can be equally applied to less vaccination, since the animal that develops an adverse reaction (e.g., hives, facial edema, anaphylaxis) from a revaccination that wasn’t needed is an example of “being sorry, not safe!”
What about all the other vaccines currently available for the dog?
They are non-core or optional vaccines that should only be given to animals that need them and they should be given as often as needed! There are also some vaccines that are not recommended for any dogs. The duration of immunity is not known for certain non-core products, the efficacy is limited or not known and the risk vs. benefit factors are not always well established nor understood. The minimum duration of immunity for Leptospira vaccines is probably less than or equal to one year, thus if required for a high risk dog, they may need to be given as often as semi-annually. Considering the low efficacy, the adverse event rate and the minimal risk for leptospirosis in many regions of the US, certain practitioners are not using the current products. However if an animal is in a high-risk environment for leptospirosis, the product to use should contain the 4 serovars (there is no significant cross protection among the 4 current serovars) and the animal should be vaccinated starting not earlier than 12 weeks of age, revaccinate in 2 to 4 weeks, revaccinate at 6 months of age, revaccinate at a year of age and then you may have to revaccinate as often as every 6 to 9 months for optimal protection. Using this program, the animal should not develop clinical disease with Leptospira, but it may get infected and shed organisms in its urine. Diagnosis of leptospirosis is best accomplished by serologic testing. The tests can diagnose disease, but not the serovar causing disease. Fortunately, it is not necessary to know the serovar to successfully treat the animal. One of the current problems with serologic testing is that some laboratories test for antibody to the serovar L. autumnalis. Dogs will often have a high titer to this serovar, which has not been shown to cause disease in dogs! Bordetella immunity may be less than one year and the efficacy for the products is not well established, but is not likely to provide more than 9 to 12 months of immunity. Many animals receive “kennel cough” (KC) vaccines that include Bordetella and CPI and/or CAV-2 every 6 to 9 months without evidence that this frequency of vaccination is necessary or beneficial. In contrast, other dogs are never vaccinated for kennel cough and disease is not seen. CPI immunity lasts approximately 3 years when given intranasally, and CAV-2 immunity lasts a minimum of 7 years parenterally for CAV-1 and about 3 years when given parenterally or intranasally for CAV-2. These two viruses in combination with Bordetella bronchiseptica are the agents often associated with kennel cough, however, other factors play an important role in disease (e.g., stress, ventilation, dust, humidity, molds, other bacteria, mycoplasma, etc.), thus kennel cough is not a vaccine preventable disease. Furthermore, KC is often a mild to moderate self limiting disease. I refer to it as the “canine cold.” My preference when a kennel cough vaccine is used is that it be an intranasal rather than the parenteral product, but some dogs will not allow anyone to administer the vaccine intranasally. Intranasal vaccines provide, in my opinion, more complete and rapid protection than a parenteral vaccine.
There is a new respiratory virus of dogs, an “equine-like influenza virus,” that first infected greyhounds in Florida in 2004. The virus caused significant respiratory disease in that initial outbreak. At the present time it is not known whether this virus, referred to now as canine influenza virus (CIV), will be an important cause of canine respiratory disease, nor if it will be an emerging disease of dogs. When and where it has occurred, like shelters and kennels, it is usually restricted to that population of dogs. It is often acute with mild to moderate clinical signs in most dogs. Mortality is low or not at all. It doesn’t readily spread to other dogs in the area, thus it will remain relatively confined to the affected group. Many questions about the role of influenza virus or for that matter, viruses other than CPI and CAV-2, bacteria other than Bordetella bronchiseptica, various mycoplasmas and other factors causing “Canine Respiratory Disease Complex” remain unanswered.
The geographic distribution of Lyme disease would suggest vaccination would only be of benefit in certain regions of the US, thus widespread use of this product is neither necessary nor desired. Although Wisconsin is an endemic area for Lyme disease, we have used very few doses of Lyme vaccines in our VMTH at the UW-Madison. We have not seen significant numbers of clinical cases of Lyme disease. However in certain areas of western and northwestern Wisconsin and eastern Minnesota, many cases of confirmed Lyme disease are seen both in vaccinated and unvaccinated dogs. Tick control for prevention and antibiotics for treatment must be used in high risk areas. Immunity to Lyme vaccines have been shown experimentally to last up to one year. My preference when a vaccine is used is the OSPA vaccines. Giardia is a relatively new vaccine that may be of value in certain circumstances, but there have not been adequate field studies to demonstrate the need nor the benefit of this vaccine. To date no one has demonstrated a benefit for coronavirus vaccine. In the vaccination guidelines from the American Animal Hospital Association, neither Giardia nor Coronavirus vaccines are recommended unless they can be proven to be beneficial for a specific animal. There are also new vaccines for snakebites (Crotalus sp.) and for periodontal disease (Porphyromonas sp.) as well as a therapeutic vaccine for treatment of canine melanomas available for dogs.
At present most canine core vaccines are given more often than needed, but a few non-core vaccines probably are not given often enough to be of benefit. Vaccines are medical products that should only be given if needed and only as often as is necessary to provide protection from diseases that are a risk to that specific animal. Lifestyle of the pet should be considered. If a vaccine that is not necessary causes an adverse reaction that would be considered an unacceptable medical procedure, thus use only those vaccines that are needed and use them only as often as needed.
Vaccination programs are changing and they will continue to change. The vaccination program must be tailored to the individual animal. Vaccines are medical products that should not be used as practice management tools. My general philosophy is to vaccinate more animals in the population, but vaccinate them only with those vaccines that the animal needs and only as often as required to maintain protective immunity. For some products vaccination may occur once or twice in a life time, whereas for other products it may be every 6 to 9 months. Be wise and immunize, but immunize wisely!
Table 1. Minimum duration of immunity for canine vaccines.
Methods used to
Canine Distemper Virus (CDV)
7 yrs/15 yrs
5 yrs/9 yrs
–rCDV Canarypox Vectored
3 yrs/4 yrs
Canine Adenovirus-2 (CAV-2)
7 yrs/9 yrs
Canine Parvovirus-2 (CPV-2)
7 yrs/10 yrs
3 yrs/5 yrs
Why Vaccination Programs are Changing?
Why, when you know from personal experience that life-long immunity exists for many human vaccines, do you have great difficulty believing a canine vaccine can also provide life-long immunity? Perhaps I and my colleagues that teach immunology to veterinary medical students have failed to explain the basics of vaccine induced “immunologic memory.” Immunologic memory is as the term implies the immune system’s ability to remember the vaccine antigens that it has seen at an earlier time in life, allowing the immune system to respond in a manner that will protect you or your dog from specific infections and/or diseases. Immunologic memory varies from disease to disease and among different types of vaccines. Immunologic memory is likely to be the same for modified live viral vaccines, as it is from natural immunity, immunity after infection or disease.
Immunologic memory is responsible for the duration of immunity that develops after recovery from natural infection/disease and after vaccination with modified live virus (MLV) or killed virus (KV) vaccines. Similarly bacterial infections and vaccines or bacterins (killed bacterial vaccines) can provide immunologic memory. Immunologic memory to bacteria is generally not as long as to viruses and, in general, immunologic memory to killed viral vaccines and to bacterial vaccines (or bacterins) is not as long lived as it is to MLV vaccines. The duration of immunity or length of immunologic memory varies among the agents causing the diseases. For example, our immunologic memory for measles virus is generally life-long. How do we know that it is life long? No one has published any controlled studies, but we know after recovering from measles infection and/or vaccination with a MLV vaccine, immunity is life-long because people rarely get measles even though they rarely receive another dose of vaccine after the final dose, prior to entering school, yet they may often be exposed to the virus. In contrast to the MLV vaccine, the killed measles vaccines that were used for a short period of time about 25 years ago failed to give life-long immunity. Many individuals receiving killed vaccines were either inadvertently infected or had to be revaccinated with a MLV when they were 15 to 20 years of age. Their exposure to virus or vaccine provided lifelong immunity. How many people do you know that were vaccinated with the modified live measles virus product, in use for approximately 40 years, or that had measles as a child, later developed measles during their life? I’m sure your answer must be very few or none! It is possible, but rarely occurs.
A very similar story to measles can be told for canine distemper virus (CDV) in the dog. CDV is in the same virus family as measles virus and rinderpest in cattle and the viruses share many similarities. As you may know, MV veterinary vaccines have been and were available until recently for use in dogs to prevent disease (not infection) caused by CDV. Those of you over the age of 50 may remember canine distemper when it was a devastating disease killing many animals with more than 50% of infected puppies often dying from CDV. If you are old enough, were observant enough and had an opportunity to follow dogs that recovered from natural infection/disease with CDV you know that dogs recovering, like their human counterpart recovering from measles, rarely, if ever, developed disease during the rest of life, even when not revaccinated. Like measles immunity in humans, immunity from canine distemper infection confers immunologic memory resulting in lifelong immunity. How do I and my older, wiser and now retired colleagues and canine infectious disease experts, Dr. Max Appel, Dr. L.E. (Skip) Carmichael, and Dr. Larry Swango know that distemper immunity is life long? We know because we had the opportunity to follow dogs that recovered from infection with CDV or puppies that were vaccinated once or twice with MLV CDV and lived for 7 or more years and never developed disease even though they were exposed to CDV via natural outbreaks or experimental challenge with CDV. We also know the vaccinated or recovered dogs had lifelong immunity because we and others performed antibody tests for years on the dogs after they recovered from infection or after puppy vaccination. These dogs all had antibody, showing that immunologic memory was present. Most of the dogs had titers that provide sterile immunity (protection from infection) much like the measles titers after vaccination or natural immunization (e.g., disease) in people. However, even if the dogs didn’t have sterile immunity but still had antibody, they had immunologic memory. An antibody titer no matter how low shows the animal has immunologic memory since memory effector B cells (long-lived plasma cells) must be present to produce that antibody. Some dogs without antibody are protected from disease because they have T cell memory, that will provide cell mediated immunity (CMI). CMI will not protect from reinfection, but it will prevent disease. When an animal is antibody negative it may have T cell immunologic memory, but I generally consider a CDV antibody negative dog not to be protected, therefore, I recommend revaccination!. Some researchers, including myself, have had the opportunity to follow the duration of immunity for dogs living in natural or experimental environments that are free of CDV and CPV-2. Why is it important that observations are made on dogs and cats that are not exposed to the virus? Because in those environments it is possible to demonstrate that immunologic memory is independent of natural or overt stimulation with the wild type virus or the vaccine virus. However, in a normal environment where infection occurs, “natural vaccination” or exposure and infection with the specific agent can and does occur at least for certain agents and in certain animals, but the infected animals do not get sick. Ironically when animals have “sterile immunity” their immune system is rarely boosted by natural exposure since infection does not occur. If infection does not occur, there is no stimulation of the specific memory T or B cells, thus the antibody titer does not increase. A severe outbreak of CPV-2 occurred in a large commercial breeding kennel, where more than 90% of puppies got sick and 50% of puppies from 4 weeks to 24 weeks of age died. However, none of more than 50 dams with sick and dying puppies had a significant increase in antibody titer, none had virus in their feces and none showed clinical signs of CPV-2 disease, all excellent indicators the dams had sterile immunity (did not get infected)!
Is immunologic memory and duration of immunity to all human viruses life-long? The answer is NO! Natural infection with many human viruses and the vaccines for those viruses provide life-long immunity (e.g., measles, mumps, rubella), whereas other viruses and/or the vaccines for them provide short duration of immunity (e.g., human cold viruses, influenza virus) and for additional viruses there is little or no immunity from infection after vaccination with commercial or experimental vaccines (e.g., HIV/herpes virus).
The three most important viral infections/diseases of dogs all provide life-long immunity. They are CDV, CPV-2, and CAV-1 (the vaccine is CAV-2). If a puppy is immunized with these three MLV vaccines (or the recombinant canarypox vectored CDV) to prevent these diseases, there is every reason to believe the vaccinated animal will have up to life-long immunity! The vaccines that prevent the diseases caused by these 3 viruses plus rabies vaccine are the “Canine Core Vaccines” or those vaccines that every puppy should receive.
An important factor contributing to lifelong immunity in addition to the memory T and B cells and the “memory effector B cells” (long lived plasma cells) of the specific (adaptive) immune system is the innate immune resistance associated with age. It is well known in all species that the young animal is more susceptible to infection and disease than a mature animal. In the case of human infections that period of increased susceptibility is often the first few years of life, especially the first year. In the puppy and the kitten it is often the first 3 to 6 months of life, but it can be up to 1 year of age that the animal is more susceptible to disease. For example, dogs less than a year of age are much more likely to develop severe parvoviral disease than susceptible (immunologically naïve) dogs and cats over one year of age, even though at both ages the animals are very susceptible to infection with CPV-2 or CPV respectively. Similarly a susceptible cat less than one year of age and especially cats less than 3 months of age are at much greater risk of becoming persistently infected with feline leukemia virus than a susceptible cat that is greater than one year of age at the time of infection. Thus innate as well as specific immune factors contribute to age-related resistance and these factors are highly complex and not completely understood. However, age related resistance plays a critical role in life-long or long term immunity. This does not imply that older dogs and cats cannot get infected and develop disease, it is that they are much less likely to get disease when compared to the younger animal and if they have been vaccinated as pups or kittens, their immunity should be excellent for up to a lifetime.
It should also be recognized that very old animals, including people, become more susceptible to disease with organisms in the environment that do not generally cause disease when younger people are infected with them. We have looked at the question of increased susceptibility to CDV, CPV-2, and CAV-1 in dogs and there is no increased disease with these viruses in very old dogs. However, that does not mean the old dogs are not at greater risk of infection with certain bacteria that only provide short term immunity. In general, bacterial immunity is shorter lived than viral immunity. For example, immunity to cholera from vaccination in humans is 6 months. Bacterial immunity in dogs to leptospirosis and Lyme disease is short lived – one year or less.
I and my colleague, Dr. Fred Scott, first proposed a three year revaccination program for dogs and cats more than 25 years ago, when we published an article in Veterinary Clinics of North America 8(4) 755-768, 1978. Today, a three year revaccination program has been recommended in the AAHA Canine Vaccination Guidelines for dogs and the American Association of Feline Practitioners Vaccine Guidelines for cats. The proposed change for revaccination with “Core Vaccines” from annual to triennial revaccination has been very controversial for many reasons, however, the reasons have little or nothing to do with “immunologic memory” or duration of immunity. No one has nor can anyone in the future, show that there is any immunologic benefit from annual revaccination with MLV CDV, CAV or CPV-2. In fact, it may even be difficult to show an immunologic benefit for revaccination at three year intervals since most animals have long term immunity for CDV, CAV-1 and CPV-2. Some among you are probably convinced that there is life long immunity to certain vaccines used in dogs and cats, but few of you after many years of performing annual revaccination are willing to take the risk, however small it may be, to adopt my puppy vaccination program–that is, to vaccinate once or twice at an age when naturally derived antibody does block the vaccine. Perform an antibody test to be sure the dog responded to CDV and CPV-2, then never revaccinate again for the life of the pet with CDV, CPV-2 or CAV-2. However, you should feel confident and recognize that adopting a three year revaccination program for CDV, CAV and CPV-2, will not increase the risk for diseases caused by these 3 viruses, just as a once every three year revaccination, rather than annual revaccination, after vaccination at 12 weeks and a year, with the killed rabies vaccines does not increase the animal’s risk for rabies. Revaccination annually with the core vaccines does increase the risk for adverse reactions!
You and your client will need to determine what vaccines and vaccination program are best for the animal. The program selected may only include core vaccines that are given once in the lifetime of the dog or the program may include all vaccines with revaccination on an annual or more often basis, or it may be a vaccination program in between these two extremes depending on what your patient and client’s needs are and what, in your medical judgment as the veterinarian, is best for each patient. Your decision should depend on the life style of the animal, its medical history, health status, age, pregnancy status and other important factors and not on using the vaccine as a practice management tool to get the clients to bring their animals in on an annual or semi-annual basis for a wellness visit.
Frequently Asked Questions (FAQ)
1. Is there a risk of over-vaccinating a pet (e.g., injecting it too often, or using vaccines that are not required for the specific pet)?
Yes–vaccines should not be given needlessly, as they may cause adverse reactions. Vaccines are medical products that should be tailored to the needs of the individual animal.
2. May I mix different types of vaccines in the syringe?
No–one should never mix different vaccine preparations in the syringe unless specified by the data sheet.
3. May I co-inject different vaccines (not part of a single commercial product) into the same animal?
Yes–but different vaccines should be injected into separate sites that are drained by different lymph nodes.
4. May I use smaller vaccine doses in small breeds to reduce the risk of adverse reactions?
No–the volume (e.g., 1.0 ml) as recommended by the manufacturer generally represents the minimum immunizing dose, therefore the total amount must be given.
5. Should the large dog (Great Dane) be injected with the same volume of vaccine as the small dog (Chihuahua)?
Yes–unlike pharmaceuticals that are dose-dependent, vaccines are not based on volume per body mass (size), but rather on the minimum immunizing dose.
6. May I vaccinate the anaesthetized patient?
It is best not to do this if possible–the patient may develop a hypersensitivity reaction and vomit, leading to an increased risk of aspiration. Also, anesthetic agents may be immunomodulatory.
7. May I vaccinate pregnant pets?
No–vaccination with MLV and killed products during pregnancy should be avoided, if at all possible.
8. May I vaccinate pets that are on immunosuppressive or cytotoxic therapy (e.g., for cancer or immune-mediated diseases, such as those with an autoimmune or hypersensitivity pathogenesis)?
No–vaccination especially with MLV products should be avoided as they may cause disease; vaccination with killed products may not be effective or may aggravate the immune-mediated disease.
9. How long after stopping immunosuppressive therapy do I wait before vaccinating a pet?
A minimum of 2 weeks.
10. May I vaccinate every week if an animal is at high risk of disease?
No–vaccines should not be given more often than every other week, even when different vaccines are being given.
11. When should the last vaccine dose be given in the puppy and kitten vaccine series?
The last dose of vaccine should be given at around 16 weeks of age.
12. May I inject a killed vaccine, followed at a later time with a MLV for the same disease?
No–the killed vaccine may induce an effective antibody response that will neutralize the MLV in the vaccine, thereby preventing immunization. It would be preferable to give the MLV vaccine first and if/when needed, revaccinate with the killed vaccine preparation.
13. May I inject a modified live intranasal Bordetella vaccine?
No–the vaccine can cause a severe local reaction and may even kill the pet.
14. May I give a killed Bordetella vaccine destined for parenteral use intranasally?
No–this will not stimulate a specific response to the Bordetella; you should give a live vaccine via the intranasal route, as specified by the data sheet.
15. Are precautions necessary when using MLV FHV-1/FCV parenteral vaccines in cats?
Yes–mucosal (e.g., conjunctival and nasal) contact with the preparation must be avoided, because the vaccine virus can cause disease.
16. Can nosodes (holistic preparations) be used to immunize pets?
No–nosodes cannot be used for the prevention of any disease. They do not immunize because they do not contain antigen.
17. Should dogs and cats with a history of adverse reaction or immune-mediated diseases (hives, facial oedema, anaphylaxis, injection site sarcoma, autoimmune disease, etc.) be vaccinated?
If the vaccine suggested to cause the adverse reaction is a core vaccine, a serological test can be performed, and if the animal is found seropositive (antibody to CDV, CPV-2, FPV) revaccination is not necessary. If the vaccine is an optional non-core vaccine (e.g., Leptospira bacterin) revaccination is discouraged. For rabies, the local authorities must be consulted to determine whether the rabies vaccine is to be administered by law or whether antibody titre may be determined as an alternative.
18. May I use different vaccine brands (manufacturers) during the vaccination program?
Yes–it may even be desirable to use vaccines from different manufacturers during the life of an animal, because different products may contain different serotypes (e.g., of feline calicivirus).
19. Should I use a disinfectant (e.g., alcohol) on the injection site?
No–the disinfectant might inactivate an MLV product, and it is not known to provide a benefit.
20. Can vaccines cause autoimmune diseases?
Vaccines themselves do not cause autoimmune disease, but in genetically predisposed animals they may trigger autoimmune responses followed by disease–as can any infection, drug, or a variety of other factors.
21. May I split vaccines in combination products?
Yes–for example, Leptospira bacterins are often the diluent for the viral antigen combination. The “viral cake” may be resuspended in sterile water, and the Leptospira bacterin be given separately at another site or time, or discarded.
22. Will a single vaccine dose of Core Vaccines provide any benefit to the dog or cat? Will it benefit the canine and feline populations?
Yes–one dose of a MLV canine core vaccine (CDV, CPV-2 CAV-2) or a feline core vaccine (FPV, FCV, FHV-1) should provide long term immunity when given to animals at or after 16 weeks of age. Every puppy and kitten 16 weeks of age or older must receive at least one dose of the MLV core vaccines. If that were done, herd (population) immunity would be significantly improved. Even in the USA with its good vaccination record, probably <50% of all puppies and <25% of all kittens ever receive a vaccine. We must vaccinate more animals in the population with core vaccines to achieve herd immunity (e.g., 75% or higher) and prevent epidemic outbreaks.
23. When an animal first receives a vaccine that requires two doses to immunize (e.g., killed vaccines like Leptospira bacterins or feline leukemia virus), and it does not return for the second dose within <6 weeks, is there any immunity?
No–a single dose of a two-dose vaccine does not provide immunity. The first dose is for priming the immune system, the second for boosting. If a second dose is not given within 6 weeks of the first, the regime must start again, making sure the two doses are given within 2 to 6 weeks. After those two doses, revaccination with a single dose can be done at any time.
24. May I give a MLV product to a wild, exotic species or to a domestic species other than to the ones which the vaccine was licensed to protect?
No–never. Many MLV vaccines have caused disease in animal species other than those for which they had been licensed. Even worse: the vaccine could be shed from those animals, regain virulence through multiple passages and cause disease even in the target species for which it had been developed. The consequences could be catastrophic! A highly effective and very safe vaccine for species that are susceptible to CDV is a canary poxvirus-vectored recombinant CDV vaccine that is available as a monovalent product for ferrets or a combination product for dogs. The monovalent vaccine is being used in many wild and exotic species susceptible to CDV.
25. May I vaccinate a puppy that is at high risk of getting CDV with a human measles vaccine?
No–due to an insufficient amount of virus, the human MV vaccine is not immunogenic in the puppy. Measles virus vaccines made specifically for the dog (sometimes combined with CDV) will give temporary protection at an earlier age than a CDV vaccine. At 16 weeks or older, the puppy must be vaccinated with a CDV vaccine, to achieve permanent immunity.
26. I know that maternally derived antibodies (MDA) can prevent active immunization with MLV vaccines–but can they also block immunity to killed vaccines?
Yes–MDA can indeed block certain killed vaccines. If the killed product requires two doses, as is often the case, and the first dose is blocked by MDA, then the second dose will not immunize. In this circumstance, the second dose will prime (if not blocked), and a third dose is required to boost and immunize. This is not true for MLV, where–in the absence of MDA–it only takes a single dose to prime, immunize, and boost. Nevertheless two doses are often recommended, particularly in young animals, to be sure one is given when MDA cannot block. That is why in the puppy or kitten series, the last dose should be given at around 16 weeks of age or later.
27. I have been told that certain canine MLV combination core products need only be given twice, with the last dose at an age as young as 10 weeks. Is that accurate?
No–it is not. No combination core product currently available will immunize an acceptable percentage of puppies when the last dose is given at 10 weeks of age. The last dose should be given at around 16 weeks of age, regardless of the number of doses given earlier. In the presence of MDA, MLV vaccines either immunize or they don’t, and the animal will be either immune or not immune–there is nothing in between. MLV vaccines do not give a little immunity with any dose when blocked by MDA.
28. For how long can a reconstituted MLV vaccine sit at room temperature without losing activity?
At room temperature, some of the more sensitive vaccines (e.g., CDV, FHV-1) will lose their ability to immunize in 2 to 3 hours, whereas other components will remain immunogenic for several days (e.g., CPV, FPV).
29. May I give the same type of vaccine parenterally and intranasally, for example the canine and feline vaccines used to prevent respiratory diseases (’kennel cough’ and feline upper respiratory disease)?
Yes–but be sure to give the product approved for that route. If you use the parenteral MLV vaccines containing FCV and FHV-1 locally, you could cause disease in the cat. If you use the killed FCV and FHV-1 vaccines locally, you would not get any immunity and might cause significant adverse reactions. If you gave the intranasal live ‘kennel cough’ vaccine parenterally, you could cause a severe necrotizing local reaction and even kill the dog, whereas giving the parenteral killed Bordetella vaccine intranasally will not immunize and may cause a hypersensitivity reaction.
However, both types of products can be given at the same time or at various times in the life of the animal. Vaccinating both parenterally and intranasally may actually provide better immunity than vaccinating at only one site. Thus parenteral vaccination provides protection in the lung but little or no immunity in the upper respiratory tract (especially local secretory IgA and CMI), whereas intranasal vaccination will engender good secretory IgA and local CMI and non-specific immunity (e.g., type I interferons), but will not always provide immunity in the lung.
30. Are there dogs and cats that cannot develop an immune response to vaccines?
Yes–this is a genetic characteristic seen particularly in some breeds, and these animals are called ‘non-responders’. Genetically related (same family or same breed) animals will often share this non-responsiveness. If the animal is a non-responder to a highly pathogenic agent, like canine parvovirus or feline panleukopenia virus, the infected animal will die if infected. If it is a non-responder to a pathogen that rarely causes death, it may become very sick but will survive (e.g., after a Bordetella bronchiseptica infection).
31. Are there mutants (biotypes or genotypes) of CDV or CPV-2 in the field that the current vaccines cannot provide protective immunity against?
No–all the current CDV and CPV-2 vaccines provide protection from all the known isolates of CDV or CPV-2, respectively, when tested experimentally as well as in the field.
32. How long after vaccination does it take for the dog to develop immunity that will prevent severe disease when the core vaccines are used?
This is dependent on the animal, the vaccine, and the disease.
a. The fastest immunity is provided by CDV vaccines–MLV and recombinant canarypox virus vectored. The immune response starts within minutes to hours and provides protection within a day to animals without interfering levels of MDA and dogs that are not severely immunosuppressed.
b. Immunity to CPV-2 and FPV develops after as few as 3 days and is usually present by 5 days when an effective MLV vaccine is used. In contrast, the killed CPV-2 and FPV-2 vaccines often take 2 to 3 weeks or longer to provide protective immunity.
c. CAV-2 MLV given parenterally would provide immunity against CAV-1 in 5 to 7 days; when given intranasally, however, the same level of immunity to CAV-1 is not present until after 2 or more weeks.
d. Time from vaccination to immunity is difficult to determine for FCV and FHV-1 because some animals will not develop any immunity.
33. Will the current ‘kennel cough’ vaccines provide any protection from disease caused by the new canine influenza virus?
No–the racing greyhounds that have been found infected and that developed disease had been routinely vaccinated 3 or more times a year with commercial ‘kennel cough’ vaccines. Canine influenza virus is antigenically unrelated to any other virus of dogs, but related to Equine Influenza Virus.
34. If an animal has gone beyond the time that is generally considered to be the maximum DOI for the vaccine (7 to 9 years for CDV, CPV-2, CAV-2; >1 year for Leptospira, Bordetella bronchiseptica; >3 years for rabies), do I have to start the series of vaccinations again (multiple doses 2 to 4 weeks apart)?
No–for MLV vaccines, multiple doses are only required at the puppy or kitten age, when an animal has MDA.
35. What can I expect from the core vaccines in terms of efficacy in the properly vaccinated puppy/dog and kitten/cat?
a. Dogs properly vaccinated with MLV or recombinant CDV, CPV-2 and CAV-2 would have > 98% protection from disease. Similarly we would expect a very high protection from infection.
b. For the properly vaccinated cat that had received MLV vaccines, we would estimate that > 98% would be protected from disease and infection with FPV.
c. In contrast, we can expect FCV and FHV-1 vaccines, at best, to protect from disease, especially in a highly contaminated environment (e.g., shelter) and protection would be seen in 60 to 70% in a high risk environment and higher in the household pet cat.
36. Are serum antibody titres useful in determining vaccine immunity?
Yes–especially for CDV, CPV-2 and CAV-1 in the dog, FPV in the cat and rabies virus in the cat and dog. Serum antibody titres are of limited or no value for the other vaccines. Assays for CMI are of little or no value for any of the vaccines for various technical and biological reasons. Such factors are less of an issue for serological tests where it is much easier to control many of the variables. However, discrepant results are still obtained, depending on the quality assurance program of the given laboratory.
37. Do puppies develop immunosuppression after the initial series of core vaccines?
Yes–if a combination product containing MLV-CDV and MLV-CAV-2 with other components is used, a period of immunosuppression lasting approximately 1 week develops, beginning 3 days after vaccination. If the combination vaccine does not contain either MLV-CDV or MLV-CAV-2, then such suppression does not occur.
For many veterinary practitioners canine vaccination programs have been “practice management tools” rather than medical procedures. Thus, it is not surprising that attempts to change the vaccines and vaccination programs based on scientific information have created great controversy and unique methods of resistance to the proposed changes have been and are being developed by certain individuals that resist change. For some practitioners the issues are not duration of immunity for the vaccines, nor which vaccines are needed for the pet, instead it is felt that every licensed vaccine should be given to every pet on an annual or more often basis. Ironically this is fostered by the fact that multivalent products with 9 or more vaccine components can be purchased for the same price or less than a product with one or two vaccine components. A “more is better” philosophy often prevails with regard to pet vaccines. On many occasions practitioners say that “I know many of the vaccines I administer probably aren’t needed but it won’t hurt to give them and who knows the animal may need them some time during their life because of unknown risk.” I have also been told by many practitioners that “I believe the duration of immunity for some vaccines like distemper, parvovirus and hepatitis is many years, but until I find another way to get the client into my office on a regular basis I’m going to keep recommending vaccines annually.” Annual vaccination has been and remains the single most important reason why most pet owners bring their pets for an annual or more often “wellness visit.” The importance of these visits for the health of the pet is exceptional. Therefore, dog owners must understand that vaccines are not the only reason why their dog needs an annual wellness visit. In fact, they must be educated that certain vaccines need not be given at all or that they need not be given very often, whereas other vaccines may need to be given more often than annually. Another reason for the reluctance to change current vaccination programs is that many people are reluctant to change anything that they have done in the past.
1. Duration of Immunity for Canine and Feline Vaccines: A Review Vet Micro 117:75-79, 2006.
Ronald D. Schultz, DVM, MS, PhD, Hon. ACVM
Professor and Chair, Department of Pathobiological Sciences,
School of Veterinary Medicine, University of Wisconsin-Madison.
Madison, WI, USA