Pet Health

Vaccine FAQ and General Information

By Wendy C. Brooks, DVM, DipABVP

Why do Baby Animals Need a Series of Shots and how many do they Need?

When a baby kitten or puppy is born, its immune system is not yet mature; the baby is wide open for infection. Fortunately, nature has a system of protection. The mother produces specific milk in the first few days after giving birth. This milk is called colostrum and is rich in all the antibodies that the mother has to offer. As the babies drink this milk, they will be taking in their mother's immunity. After the first couple of days, regular milk is produced and the baby's intestines undergo what is called closure, which means they are no longer able to take antibodies into their systems. These first two days are critical to determining what kind of immunity the baby will receive until its own system can take over.

How long this maternal antibody lasts in a given puppy is totally individual. It can depend on the birth order of the babies, how well they nursed, and a number of other factors. Maternal antibodies against different diseases wear off after different times. We do know that by 16 to 20 weeks of age, maternal antibodies are gone and the baby must be able continue on its own immune system.

While maternal immunity is in the puppy’s system, any vaccines given will be inactivated. Vaccines will not be able to "take" until maternal antibody has sufficiently dropped. Puppies and kittens receive a series of vaccines ending at a time when we know the baby's own immune system should be able to respond. We could simply wait until the baby is old enough to definitely respond as we do with the rabies vaccination but this could leave a large window of vulnerability if the maternal antibody wanes early. To give babies the best chance of responding to vaccination, we vaccinate intermittently (usually every 2 to 4 weeks) during this period, in hope of gaining some early protection.

When a vaccine against a specific disease is started for the first time, even in adult animal, it is best to give at least two vaccinations. This is because the second vaccination will produce a much greater (logarithmically greater) response if it is following a vaccine given 2 to 4 weeks prior.

If a Vaccine Lasts a Person his or her Whole Life, why do I have to Vaccinate my Pet Annually?

In the U.S., vaccines are licensed based on the minimum duration they can be expected to last. It is expensive to test vaccines across an expanse of years and it is not generally done. We know most vaccines last at least one year and have not been willing to take a chance on whether they might last longer without knowing for sure.

It is also important to realize that some diseases lend themselves to prevention through vaccination while others do not. For a vaccine to generate solid long-lasting immunity, the infection must be fairly generalized to the entire body (like feline distemper or canine parvovirus) rather than localized to one organ system (like kennel cough or feline upper respiratory viruses). Vaccination for localized infections tends to require more frequent boosting whereas there is potential for vaccination for systemic disease to last for many years.

Since the mid-1990s most veterinary teaching hospitals have restructured their vaccination policies to increase the duration of some vaccines from one year to three years. Many private veterinarians are following those guidelines for these vaccines. The important thing to realize is that this kind of extension is not possible in all situations or for all vaccines.

What do I do if my Pet Skips a Year of Vaccination?

It depends on the vaccine and the hospital. Hospitals are likely to have different recommendations as vaccination policy tends to be individualized to the practice and its geographic location. At some hospitals, recommendations for adult animals who skip an annual vaccine include:

Feline distemper (FVRCP), feline leukemia (FeLV) - Vaccinate normally. It is not necessary to re-start the initial series.
Rabies A 3-year vaccine can be given anytime after the initial one-year vaccine. This means that if a year is skipped, the next rabies vaccine given will still be a 3-year vaccine.
Feline infectious peritonitis If you skip a year and want to be assured that your pet has good titers, the initial series should be restarted.
Canine distemper, canine parvovirus , nasal Bordatella (kennel cough) - Vaccinate normally. You do not need to restart the initial series as though the pet is starting over from the beginning.
Canine coronavirus - some veterinarians do not feel this infection is significant in adult dogs; however, if you wish to maintain strong titers and have skipped a year, you can restart the initial series.
Lyme disease Should a dog in a geographically affected area skip a year with this vaccine, some veterinarians recommend restarting the initial series.
Rattlesnake bite vaccination Because of the complex nature of snake venom, vaccination is recommended every six months. If you have skipped an entire year it would probably be good to restart the initial series of two vaccines (three for smaller dogs and three for larger dogs).
Periodontal bacterial (Porphyromonas) vaccine: Many veterinarians are waiting for more specific recommendations come from the manufacturer, but in the meanwhile some veterinarians pick up this series with the single annual booster and go from there.

What Vaccines Should I get for my Pet?

What vaccines are recommended to an individual pet depend on many factors: what kind of exposure to disease does the animal have, what diseases are common in the area, what kind of stress factors are in the home situation, etc. When you consider the multitudes of vaccine types and combinations and the many different situations dogs and cats live in, it is not too surprising to find that almost every veterinarian recommends a different group of vaccines. The best advice is to hook up with a veterinarian that you trust and go with their recommendation. If you wish to determine what shots you want on your own, hopefully this web site will be of use.

What Vaccines Should I get if my Pet is Indoors almost Completely?

Both the American Association of Feline Practitioners and the American Animal Hospital Association have published guidelines for vaccination. Vaccinations are divided into “core” vaccines that every pet should have, and “non-core” vaccines that a pet should have depending on exposure risk.

For cats, core vaccines are the basic distemper shot (FVRCP) and rabies vaccine. Many people are surprised that rabies is a core vaccine and is considered important even for indoor-only cats but when you consider the consequences of rabies exposure (which can certainly happen indoors) and the legal consequences of owning a biting animal (what happens to the animal generally is dependent on its vaccine status), it is not hard to see why this vaccine is important.

For dogs, core vaccines are the basic distemper shot (DHLPP) and the rabies vaccine. Since dogs do go outside for walks, for grooming, to the vet’s office etc. most veterinarians recommend vaccine against kennel cough for canine patients.

What is the Difference Between a Live and a Killed Vaccine?

These terms apply to vaccine against viral infection.

The goal of vaccination is to present the virus in question to the patient’s immune system in as natural a way as possible so as to best mimic the stimulation obtained by natural infection, yet skip the illness experienced by the patient.

There are two ways to achieve this goal. One way is to use killed vaccine. Here, large amounts of dead virus are injected into the patient. They filter into the immune system and lead to stimulation. The other way is to use a live virus that has been modified such that actual disease does not result in infection. By using live virus, a more natural stimulation is obtained as the live viruses follow through the same steps of replication that the real ("street") virus would.

Which method is best remains somewhat controversial. Some experts feel that killed vaccine is best as there will never be a chance that the patient can contract the actual disease from the vaccine if a killed vaccine is used. Proponents of live vaccines have been able to demonstrate that far stronger immunity can be generated by the live vaccines. While our hospital stocks some killed vaccine available upon request, we feel that the live vaccine indeed produces better protection and this is what we use on a routine basis unless we have an option to use a recombinant vaccine (see below).

Can a Pregnant Pet be Vaccinated?

It is important that live vaccines (see above) NOT be used in pregnant pets. This is because a "modified" virus that will not cause illness in the mother may still be strong enough to infect the unborn puppies or kittens. Killed vaccines may be given during pregnancy though, as a general rule, it is best not to give any medical treatments during pregnancy if it can be avoided. While the administration of killed vaccines is commonly performed in large animals and food animals, it is not routine for dogs or cats.

Can I give Vaccines Myself?

It is physically possible to give vaccines yourself if you know how to give a subcutaneous injection. In many areas, pet vaccines are considered over-the-counter medications and you can get them from your local pharmacy or by mail order. Some veterinarians do not recommend this practice for the following reasons:

It may be difficult for you to properly dispose of the needles.
If there is any type of acute allergic reaction, you will not be prepared to address it.
In cats, there are specific guidelines regarding where vaccines should be placed. This makes the process trickier especially with uncooperative cats. You may get bitten. If you do not know where to give each type of vaccine, you could be increasing the risk of vaccine-site tumor formation.
You may not have kept proper records of vaccination should proof of vaccination be needed. Facilities requiring proof of vaccination may be unwilling to accept your own word that your pet is vaccinated adequately.
Modified live vaccines are somewhat sensitive to proper storage. They cannot be mixed up in advance and their components must be kept at the proper temperature. This may be difficult depending on how vaccine is transported to your home.

If you are looking for a low-cost method of vaccination, consider a low cost vaccination clinic rather than trying to give vaccine on your own.

Why is a Feline Leukemia Test Required Prior to Vaccination?

The feline leukemia virus has potential to be latent in a carrier cat without any signs of illness, and this carrier state can persist for years. During this time, the cat is contagious and at risk for numerous problems. Many people want to skip the test to save money but, in fact, it is of great importance to know if a cat is harboring this infection. Knowing that a cat is positive allows you to save money by not unnecessarily vaccinating for feline leukemia. Furthermore, if an owner is aware of a cat's positive status, the pet can be kept away from other cats thus preventing the spread of the disease. An owner can prepare financially for expected treatments needed for this cat if the owner is aware of the positive test. We feel strongly that testing is important whenever a new cat is obtained as a pet.

What is a High Titer Parvo Vaccine?

A high titer parvo vaccine is a type of modified live vaccine that uses especially large amounts of virus to stimulate the immune system. The most important advantage of this new type of vaccine is its ability to produce strong immunity in puppies at an earlier age than was previously possible. Regular modified live vaccine is considered able to produce immunity by 16 weeks of age with another 5% or so of puppies becoming immune if vaccination is continued through age 20 weeks. The high titer vaccines appear able to reliably produce immunity by 12 weeks of age, though many hospitals use them through age 16 weeks to ensure good immunity. High titer vaccines are considered to be state of the art.

What is a Recombinant Vaccine and is it really Better than the other Available Vaccine Types?

For generations, we classified vaccines as either "killed" or "modified live" (see above). With the advent of genetic engineering, there are now new vaccines that do not fit this classification: the recombinant vaccines. The USDA classifies recombinant vaccines into four groups:

Category I: Subunit Vaccines
Remember that the immune system is stimulated by the shape of a foreign protein. (Your body knows what protein shapes are natural to its own cells and will attack most other shapes. Unfortunately, some organisms, such the AIDS virus and the feline leukemia virus, have protein shapes that actually turn the host immune system off!) When it comes to designing a vaccine against an organism, one thought is that it is not efficient to use the entire "dead body" of the organism to stimulate the immune system. The idea here is that it would be more efficient to use only the protein shapes that are stimulatory to the immune system. Shapes that might be detrimental could be omitted as could be any neutral shapes.

A subunit vaccine contains only the proteins that stimulate the immune system to attack. By manipulating DNA that codes for these most stimulatory proteins, we can mass produce a purified solution and immunize with only the antigen we want and no extraneous antigens. The Genetivac brand of Feline Leukemia Vaccine (not currently on the market in the U.S.) is an example of a subunit vaccine.
Category II: Gene Deleted Vaccines
The traditional modified live vaccines take the infectious agent and change it chemically or mutationally so that it can still infect the host (and thereby stimulate the immune system) but no symptoms of disease result. The stimulation that results is generally excellent as the immune system is stimulated in exactly the same sequence it would be in a natural infection, and currently modified live vaccination is felt to be far superior in efficacy relative to killed virus vaccination. Concern has been voiced, however, regarding the possibility of live virus reverting to its virulent form.

The gene deleted vaccines address this concern. They are, in a way, modified live vaccines with the modification being that the genes allowing for creating physical illness have been deleted.
Category III: Vectored Virus Vaccines
Here, the DNA for the stimulatory proteins described in the subunit vaccine area is inserted into harmless viruses. The live harmless virus is able to provide a natural immune stimulation and will express the stimulatory proteins native to a harmful virus. In this method, one gets the benefits of the modified live vaccine with the benefits of the subunit vaccine.

Merial created a distemper vaccine for dogs using this technology (though the other virus components of this 5-way vaccine are still of the conventional "non-recombinant" type.) Also, this technology is currently in use to vaccinate wildlife against rabies, using edible bait laced with vaccine. The new PUREVAX rabies vaccine for cats is also a vectored virus vaccine, as is the Merial Lyme disease vaccine.
Category IV: Other
At this time there is only one vaccine type in the "other" category: the "naked DNA or RNA" vaccine. Here, DNA from the infectious agent is injected into the host. No proteins. No putting the DNA inside any viruses. Just plain raw DNA.

This DNA is taken up by the local muscle cells and soon the proteins coded for by this DNA are being produced. The immune system thus receives its stimulation without risking exposure to an infectious agent of any kind.

So why are these vaccines better than the traditional ones? The chief benefit seems to be the reduction in vaccine reactions since there are less extraneous proteins to cause unnecessary immune stimulation. This makes vaccination not only safer but less likely to be associated with unpleasant fever or muscle inflammation. With respect to the recombinant rabies vaccine for cats, recombinant technology has allowed this vaccine to be manufactured without adjuvants. Adjuvants are chemicals that stabilized killed vaccines and are felt by many to be linked to inflammatory vaccine side effects as well as to the development of the vaccine associated fibrosarcoma. Recombinant vaccines represent the cutting edge of vaccine technology in both veterinary and human medicine.

Can Vaccines Hurt my Pet?

Some muscle soreness, lethargy and mild fever persisting for a day or two are considered common reactions to stimulation of the immune system. Vaccine reactions beyond this are unusual but possible. Allergic reactions characterized usually by facial swelling and hives are a strong sign that special care should be taken in administering vaccinations. Since allergic reactions potentially can become worse with each episode, it is important to take heed of these signs as severe reactions can result in shock or even death.

Another reaction that has received tremendous press lately is the vaccine-induced fibrosarcoma, a form of cancer in the cat (see the next question).

Can Vaccines Cause Cancer?

The fibrosarcoma is an especially aggressive form of cancer that can affect cats spontaneously or by viral induction via the feline sarcoma virus. Recently, fibrosarcomas have been removed from areas of the body typically used for vaccination and, to the surprise of the veterinary profession, particles of aluminum-based vaccine ingredients (called adjuvants) were discovered within the tumor. The working theory is that vaccination may induce this form of cancer in rare cases (between 1 in 1000 and 1 in 10,000 cats). The killed feline leukemia vaccine and the killed rabies vaccine have been implicated as being more likely to be involved. The problem is definitely not a matter of simply changing to non-aluminum based adjuvants but is more complicated. A list of preventive measures has been issued by most veterinary associations.

Can Over-Vaccination Cause other Diseases?

As mentioned, in the mid-1990s recommendations for annual canine distemper and feline distemper vaccination shifted to every 3 years for these vaccines. The reason for this is not that annual vaccination was found to be harmful; it simply became accepted as unnecessary.

Many people have speculated that annual vaccination is responsible for cancer, immune-mediated diseases, kidney disease, and most common ailments of senior dogs and cats. So far, there is no clear evidence that annual vaccination has increased the incidence of any specific health problems.

How can I Have my Pets Vaccinated at Low Cost?

Vaccination is an important part of a pet's health and it should not be skipped. If cost is a problem there are several approaches you can take but each has advantages and disadvantages.

OPTION ONE: Omit the Examination and Choose Vaccination Only
Prices vary tremendously from veterinarian to veterinarian. Some veterinarians are not comfortable administering vaccinations without completely examining the pet first. Others allow you the option of coming in for vaccination only. Obviously, an exam at least annually is of crucial importance to an elderly pet or a pet with a known history of illness and you never know when your veterinarian will pick up an important finding but if money is tight, skipping the exam is an option.
OPTION TWO: Vaccinating your Pets Yourself
In most states, vaccines are available over-the-counter at the regular pharmacy at substantial savings. Of course, this presupposes that you know how to administer the subcutaneous needle and that you are comfortable disposing of the syringe. Many people find it worth it to pay more for a trained professional to administer the shot but if you have the training, this is an option that can save you money.
OPTION THREE: Vaccination Clinic
These clinics are springing up everywhere to provide streamlined "shots only" service. These clinics may be mobile (traveling monthly or weekly to your local feed or pet supply store) or may be located in your own regular veterinarian's office. Here are some tips on what to look for in a clinic:

Are they using disposable needles?
You probably do not want to have your pet experience a needle that has been dulled on a previous patient or possibly inadequately re-sterilized.

Is the clinic using the latest guidelines to avoid vaccine-induced fibrosarcomas?
This might be a good indicator of whether the clinic is up-to-date in its quality control. See more information on prevention of vaccine-induced fibrosarcomas.

Do they seem simply interested in selling you the maximum number of vaccines or do they seem genuinely interested in informing you on which vaccines you do and do not need?
Many vaccine clinics pay their staff commission for the number of vaccines sold.

Is your regular veterinarian's office sponsoring the clinic?
If they are, this will solve a lot of confusion about keeping vaccine records straight at your vet's office and will avoid the confusion of getting vaccine recommendations from different veterinarians.

Are the vaccines already drawn up or are they mixed fresh while you are present?
Modified live vaccines are sensitive about storage, especially after they are reconstituted. A mobile clinic must contend with the inherent difficulties of refrigeration. You do not want to use a vaccine that may have been reconstituted perhaps hours before.

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