Ron Hines DVM PhD 9/8/07

Adjuvants are compounds that are added to vaccines in an attempt to increase their effectiveness. I no longer use them because they seem to have many side effects. At least one company, Intervet , offers a non-adjuvanted 3-year cat vaccine. This is the vaccine that I use in cats. It contains none of the adjuvants that may cause cancer or immunological disease later in life. An even better choice might be Heska's intranasal vaccine which requires no injection. A feline leukemia vaccine containing no complete virus and no adjuvants is Merial's Purevax products which uses recombinant canarypox vector vaccine technology. I suggest your pet receive a rabies vaccine that also contains no adjuvants. Even non-adjuvanted injectable vaccines are not risk-free. If your cat has had prior vaccine reactions, think seriously before having any vaccines administered.

It takes a full 14 days after vaccination for the cat to be fully protected.

Until recently, it was standard veterinary practice in the United States to vaccinate cats yearly for feline panleukopenia (FPV, aka feline distemper, feline enteritis), feline calicivirus (FCV) and feline rhinotracheitis (feline herpesvirus-1orFHV). Many practitioners also administer yearly vaccinations against Chlamydia psittaci (CP) and feline leukemia and most States also require that cats receive a yearly rabies vaccination. In high-stress, multi-cat households or roaming cats I sometimes also administer a vaccine yearly against infectious peritonitis (FIP) and I also suggest a vaccination against feline immunodeficiency disease.

How Vaccines Work:
Vaccines stimulate the immune system to produce antibodies (titer) against a disease organism so that the cat is protected against various pathogens in its environment. If the immunized cat is later exposed to the infectious agent, these antibodies react quickly to attack and neutralize the disease. Cats also possess “memory” cells that mount a rapid attack against virus and bacteria that they were once exposed to– even when antibody titer is low or undetectable.
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Kitten Vaccinations:
When it comes to kittens most veterinarians are in agreement. Kittens should receive their FPV, FCV, FHV and CP vaccinations at 7-9 weeks of age. To be sure kittens are well protected against these diseases, at 12-13 weeks of age and at 16-18 weeks of age they receive additional boosters of these vaccines as well as vaccinations against feline leukemia (FLV) and sometimes feline immunodeficiency virus (Feline Aids, FIV). I generally administer a rabies vaccination at 12-14 weeks of age as well. Rabies, FLV, FIV, and Chlamydia psittaci are killed products. The rest of these vaccines are freeze-dried living virus that have been grown in tissue culture in a way that makes them non-pathogenic (weak) i.e. unable to cause disease. Actually, a single injection, at the right time, of all these live products imparts good, long lasting immunity to all of these diseases. The problem is that kittens absorb antibodies against these diseases from their mothers. Depending on the level of immunity in the mother, this transient parental immunity in the offspring interferes with the kitten’s ability to produce its own long lasting immunity to these diseases. In some kittens, parental immunity is low enough that by 8-12 weeks the vaccinations can work. In others, parental immunity interferes with the action of the vaccine for up to 18 weeks. The tests that determine parental immunity levels in kittens are expensive and rarely run. So because we do not know just when to vaccinate we give a series of three or four injections so that at least one of them will work. Another problem is that the immune system of young cats is sometimes immature and incapable of mounting a good antibody (titre) defense to the vaccines.

Adult Immunizations:
Once we are sure we have a protected kitten we need to decide how often we should revaccinate our cat to keep immunity at protective levels. Until recently, veterinarians simply gave all cats booster shots every year. This is what the vaccine manufacturers suggested. Besides, it brought our clientele back to our animal hospitals yearly, which increased our opportunity to detect other problems early before the owners were aware of them. Most veterinarians do a thorough physical examination on pets at the time of their yearly vaccinations and we often detect problems during these exams. By law, most states require a yearly rabies vaccination - even though studies have shown that many of the rabies vaccines we use give us three years of protection.

Many veterinarians, myself included, were suspicious that the vaccines we used were giving much longer periods of protection than one year. We knew this because we never saw feline panleukopenia, feline leukemia or calicivirus infection in cats that had been vaccinated - even many years earlier. Part of the problem involves the typical fee structures of veterinary practices. We tend to undercharge for complex surgery and subsidize those procedures with the money we earn on yearly vaccinations. I do not know how this practice came about but it has existed at least since the 1950’s. There was also an incentive for vaccine manufacturers to sell more vaccine if boosters were recommended annually as well as a one-year mindset among the bureaucrats that staff the USDA Center for Veterinary Biologics that dictate vaccination protocols. These are the same deep thinkers that mandate a two-year expiration date on a vial of water.

How Frequently To Immunize:
For most cats, vaccination induces a serologic response (titer) to all three viral antigens that lasts for an extended period – in many instances four to seven years or more. Most recently, the Pfizer drug company conducted a series of experiments on their brand of cat vaccine (Felocel-4)(1). In another study (2) scientists found protective antibodies to FCV and FHV lasted for three years or more and protection against FPV lasted up to the seven and a half years – pssibly longer. They found that blood titers of 1:4 or greater protected the cats from FPV while titers of 1:2 or greater protected against FCV. Another group of scientists (3) found that if any detectable antibodies were present against FPV, FCV or FHV the cats could not be given the disease even when purposely exposed to it. The titers they found protective were 1:10 or greater for FPV and 1:8 or greater for FCV and FHV. For FPV, of the 31 cats that had not received panleukopenia vaccinations within four years previous, more than 93.9% were still immune. Of the 33 cats that had not had feline calicivirus vaccinations within four years or more 100% showed immunity. Of the 28 cats that had not received rhinotracheitis vaccination for four years or more 84.8% were immune. Rhinotracheitis (HV) is the least effective of the vaccines - even one year after vaccination only 88.2% of cats were immune. At least one company, Intervet, offers a 3-year cat vaccine. This is the vaccine that I use in cats. It contains non of the adjuvants that may cause cancer or immunological disease later in life.

Based on these studies I recommend that kittens continue to receive the series of vaccinations we currently give and that they then receive annual booster vaccinations against feline panleukopenia, feline rhinotracheitis and feline calicivirus for two years. After that, vaccination every four to five years should well protect them. Indoors cats, which make up about two thirds of the cats I see, need less frequent boosting than cats that go out of doors. No two vaccine manufactures produce identical products so you should not assume that the brand your veterinarian uses induces this long an immunity - but I suspect they all protect well over a year. An exception would be cats living in large multi-cat household or catteries that are under heavy stress. Stress is known to depress the immune system. I do not know the answer as to what to do with cats that are positive for Feline leukemia or feline immunodeficiency disease. They should however, be kept isolated indoors where disease exposure is should not be a problem. The most effective vaccines are against feline panleukopenia and feline calicivirus. About 98% of cats are protected by these vaccines. The least effective is against feline rhinotracheitis – about 88% of cats are protected by this vaccine if it is given before the cat is naturally exposed to the disease. The problem is that so many kittens already have signs of rhinotracheitis before we have the chance to give them their kitten shots. Then, of course, the vaccine does not work. Rhinotracheitis passes rapidly through carrier queens, unprotected cats at animal shelters and catteries. This often occurs before their personnel has a chance to vaccinate them or for the animals to develop immunity.

Within the last decade a link has been seen between vaccination in cats and injection-site cancer (fibrosarcoma). About 0.5-6.5 cases/10,000 cats will develop this tumor at the site of a past vaccine injection. This is a very stubborn invasive tumor. It is reason enough to space booster vaccinations farther apart than every year. Inflammation is often a prelude to cancer. Cats react with inflammation at any injection site – even to sterile water. And sometimes a plug of skin is carried down with the needle into the deeper tissues causing further inflammation. To prevent this, all cat injections should be given subcutaneously through narrow 25 gauge needles that cause the least damage possible. It is a bit harder for veterinarians to use these small needles but it is quite worth the effort. There is also a possible link between vaccinations and autoimmune diseases in cats. I know of no studies that have been done on this phenomenon but we have all seen enough cases to make us suspicious of a link.

I know of no work that has been done on feline leukemia vaccine. I do know that I have never seen feline leukemia in a cat that received two years of any of the feline leukemia vaccines on the market today. Perhaps this is pure chance – perhaps not. There is also some evidence that older cats are less susceptible to FLV. The Feline Immunodeficiency vaccine is too new on the market for us to make a judgment as to its efficacy.

There are other risks involved in too frequent vaccinations. For one, the immune system of your cat is stressed by these vaccinations. Occasional cats develop allergic reactions, facial edema, enteritis, lethargy, fevers, pruritis, nausea, coughing. We also suspect that vaccinations can trigger certain autoimmune diseases. Occasionally these reactions are life threatening. Vaccines contain many ingredients besides the dried virus. Some of these, antibiotics and adjuvants (enhancers) are implicated in vaccine reactions. In cats that have had prior history of vaccine reactions I often do not give yearly vaccinations. I feel the risks outweigh the benefits and write a letter for the owners to this effect. If I am suspicious that a cat might have a reaction to a particular vaccine I pre-administer antihistamines (Benadryl) and give a minute test dose of 0.05ml. If the cat is normal thirty minutes after the test dose I give it the remaining one-milliliter. I limit yearly or every two-year vaccinations for the four “core” diseases to “higher risk cats”. Higher risk cats are cats that roam or take unsupervised strolls; cats that play with other cats not from their household, cats that have contact with wild animals, or swim and drink from pools puddles and streams. Other cats are more at risk because the attend cat shows, large grooming and boarding facilities. About one third of the cats I see fall into this higher risk category.

Determining The Need For Booster Vaccinations By Serum Titer:
It is possible for your veterinarian to remove a serum blood sample from your cat every year and have it tested for antibody (titer) against these diseases. If the antibody is there, the cat does not need a booster vaccination against that disease. This is a procedure that will become more widely accepted as time goes by. A lot of veterinary laboratories already offer this service http://www.antechdiagnostics.com/.

Newer, Safer Vaccines:

Several Pharmaceutical companies have or are in the process of marketing intranasal vaccines for cats which are applied into your cat's nose. The Heska Corporation of Ft. Collins Colo. has just launched two new intranasal vaccines designed to protect cats against feline panleukopenia, rhinotracheitis and calicivirus. (Feline UltraNasal FVRC). These vaccines are an excellent way to avoid the dangers of vaccine injection. A newer ,non-adjuvanted subunit/canary pox feline leukemia vaccine is now marketed by Meriel. In 2005 then introduced a transdermal jet injection system (VetJet) that eliminates the need for a needle. This might lessen the rare occurrence of injection site tumors in cats because the injection tract is very narrow.

1) Mouzin D.E., Lorenzen M.J., Haworth J.D., King VL. Duration of serologic response to three viral antigens in cats. JAVMA, Vol. 224 61-66, 2004

2) Scott F.W., Geissinger CM. Long-term immunity in cats vaccinated with inactivated trivalent vaccine. Am. J. Vet. Res.
Vol. 60 652-658,1999

3) Lappin M.R., Andrews J., Simpson D. et al. Use of serologic tests to predict resistance to feline herpesvirus1, feline calicivirus and feline parvovirus infection in cats JAVMA Vol 220 38-42, 2002.

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