The Cat Group strongly supports the routine vaccination of all cats against major infectious diseases. Vaccination of cats has played a vital role in reducing the prevalence and severity of several feline diseases including some that are associated with a high rate of mortality. Despite the success of vaccination, these diseases are still present in cat populations, and thus a failure to maintain routine vaccination will place cats at risk of contracting disease. Currently approximately one third of the pet cat population in the UK is regularly vaccinated, and the Cat Group strongly believe that a much wider use of vaccination would be of benefit both to individual cats, and to the wider feline population, in further reducing the prevalence and severity of disease.
Despite the success and importance of vaccination, the Cat Group recognises that adverse reactions do occur to vaccines, and that this is a cause for some concern. Nevertheless, serious adverse reactions are extremely rare and the benefits of vaccination far outweigh the risks involved. However, as vaccination inevitably carries some risk of side-effects the Cat Group support the use of discriminatory vaccine policies, where vaccines are not used unnecessarily in individual cats and the risks and benefits of vaccination are carefully evaluated and discussed for each cat.
The Cat Group recognises that recent scientific evidence has questioned the necessity for routine annual booster vaccination of cats against all diseases. It is likely that vaccine-induced immunity, for some diseases at least, will last significantly longer than 12 months, but this will vary between the different diseases and between different vaccines, as well as between individual cats. There is currently insufficient scientific evidence to determine the optimum frequency of vaccination for any individual disease. The Cat Group therefore supports owners being given informed choice both about which vaccine components should be used, and the frequency of booster vaccinations, based on current best evidence.
Several vaccines are currently in use in the UK. The following is a brief description of the diseases for which vaccines are available. It should be noted that vaccines for other diseases are available in some countries, but not currently in the UK.
Feline infectious enteritis (FIE, feline panleukopenia, feline parvovirus)
Feline infectious enteritis is a disease caused by infection with feline parvovirus. This virus can be responsible for a severe and often fatal form of gastroenteritis. Affected cats typically show signs of severe vomiting and diarrhoea, but the disease may be so severe as to cause sudden death with no other signs. In addition to enteritis, the virus can also cause neurological disease (brain damage) in kittens infected before or shortly after birth. The virus also affects the bone marrow and lymphoid tissue suppressing the production of white blood cells. In cats that survive disease, recovery can be prolonged. The virus is very resistant and can survive for long periods in the environment. Vaccination against feline infectious enteritis has been extremely successful. Although feline parvovirus is still a prevalent virus, vaccination confers a high level of protection against infection and subsequent disease.
Feline herpesvirus (FHV-1) and feline calicivirus (FCV) – Cat 'flu
Two viruses – FHV-1 and FCV – are responsible for the majority of cases of cat 'flu, or acute upper respiratory tract disease. These viruses are extremely common, and infection results in a variety of signs including sneezing, nasal discharge, conjunctivitis, ocular discharge, mouth ulceration, pharyngitis (inflamed throat), coughing and, rarely, pneumonia and skin infections.
Disease following infection varies from being mild to very severe, and occasionally fatal. Recovery may take from a few days to several weeks, and severe disease can result in permanent damage to the nose or eyes. Following infection many cats remain carriers of these viruses (although they may no longer show any signs of disease), thus acting as a source of infection for others. The viruses do not survive long in the environment so infection is usually acquired through close contact between cats.
Vaccination against FCV and FHV-1 has a major role to play in protecting cats from disease or reducing the severity of disease in cats. However, vaccination does not necessarily prevent infection with these viruses (partly because there are many different strains of FCV), and vaccinated cats can also become carriers of the viruses and pass them on to others.
Feline chlamydophilosis ( Chlamydophila felis, feline chlamydophila infection)
Chlamydophila felis was formerly known as feline Chlamydia psittaci. This is a type of specialised bacterium that causes mainly conjunctivitis in cats. The bacterium is very fragile and cannot survive in the environment, so is transmitted by direct contact between cats. Infection is most common in kittens and young cats from multicat household environments. Infection results in mild to severe conjunctivitis and ocular discharge. Mild sneezing and nasal discharge can also be seen.
Vaccination against chlamydophila affords protection against disease or severe disease but as with FCV or FHV-1 vaccination, the chlamydophila vaccine does not necessarily prevent infection with the organism and thus mild disease can occur in a vaccinated cat.
Feline leukaemia virus (FeLV)
Infection with FeLV frequently results in persistent, life-long infection (also known as ‘persistent viraemia'). Cats that remain infected with the virus generally develop fatal disease. Most will die or be euthanased within three years of being diagnosed with the infection. Persistent FeLV infection causes disease through a variety of different means, but most cats die due to immunsuppression caused by the persistent infection, progressive anaemia, or through the development of tumours (lymphoma) or leukaemia.
FeLV is a very fragile virus and cannot survive outside of the cat for long. Transmission of the virus is therefore by direct contact between cats, and mainly via exchange of saliva. Transmission is inefficient though, and it is thought that prolonged close contact between cats is generally required for this to occur. Infection with FeLV has been controlled by testing for the virus (using blood tests) and removing or isolating infected cats. In recent years, FeLV vaccines have been introduced which offer protection against infection and can therefore be used to protect cats at risk of being exposed to infection. However, vaccination may not protect all cats.
Cats can be infected with the bacteria Bordetella bronchiseptica. This is probably most familiar to pet owners as one of the major causes of ‘kennel cough' in dogs. In cats, infection with bordetella most often causes signs of upper respiratory tract infection (sneezing and nasal discharge), although this bacteria has been isolated from some cases of pneumonia, especially in kittens. Infection is more common in multi-cat households and the bacteria can be spread between dogs and cats. Although various studies have suggested quite widespread exposure to bordetella in cats, it is not generally considered to be a common cause of significant disease. Infections are usually self-limiting and additionally will respond well to appropriate antibiotic therapy. An effective intra-nasally administered vaccine is available for cats, and can be used if situations arise where it is considered important to protect cats from infection.
Rabies is caused by a virus which, among other effects, attacks the nervous system causing a potentially fatal disease. The virus can infect almost all warm blooded animals but is most commonly found in dogs, foxes, bats, cats and monkeys. Infected animals can transmit infection to humans via bites, as the virus is excreted in saliva.
Rabies is prevalent in many countries, but the UK is rabies-free and quarantine has been used for animals entering the UK to ensure that rabies does not inadvertently enter the country through the transport of pets.
Vaccination can be used to protect animals (including cats) against rabies infection. The recently introduced Pet Travel Scheme (PETS) allows entry of pet animals from certain countries into the UK without the need for quarantine so long as they meet certain conditions which include having the pet microchipped (for identification purposes), having the pet vaccinated against rabies, and having a blood test to ensure the vaccine has given a satisfactory level of protection. Full details of the PET scheme is available on the DEFRA web site: www.defra.gov.uk
A number of different vaccines are available in the UK from different pharmaceutical companies. Most vaccines are very similar although there are some differences.
All vaccines are designed to provoke an immune response against the organism responsible for the disease, such that if the cat is subsequently exposed to the organism, the immune response will protect against infection and/or development of disease. Vaccines may contain the whole organism (virus, bacterium) or only certain proteins from the organism (so called ‘subunit' or ‘recombinant' vaccines). Where only certain proteins from the organism are used, these are chosen because they are believed to be the proteins responsible for producing a protective immune response.
Vaccines may be either killed (containing no living organism) or can be ‘modified live' – containing a live form of the organism that is able to replicate but, by modification, has been rendered incapable of causing disease. Killed vaccines usually contain an ‘adjuvant' – an ingredient that is combined with the killed organism to help stimulate a good immune response. Modified live vaccines do not require an adjuvant as the replication of the organism itself stimulates a good immune response. Live vaccines are generally not recommended for use in pregnant queens and ideally should be avoided in immunosuppressed cats.
Various killed and modified live vaccines are available for feline infectious enteritis and cat ‘flu' in the UK . Currently only a modified live intranasal bordetella vaccine is available, and only killed vaccines are available for chlamydophila and FeLV vaccines are either killed or virus-vectored (contain parts of the FeLV virus inserted into another live virus for the vaccine). Licensing requirements for vaccines in the UK ensure rigorous testing for quality, safety and efficacy before they can be used in cats.
All the vaccines currently licensed for use in the UK are given by injection – by either the sub-cutaneous (under the skin) or intramuscular route – with the exception of the bordetella vaccine which is given as drops in the nose (and requires only a single dose). Kittens generally require two vaccines given 3 to 4 weeks apart to stimulate a good immune response, and vaccination usually starts at around 9 weeks of age. Following the initial vaccine course, booster vaccinations (single injections) given at regular intervals are recommended to maintain a good level of protection.
The two vaccinations given to kittens are recommended to ensure a good immune response and to overcome the problems of maternal antibodies. Kittens receive antibodies from colostrums (the milk which the mother produces soon after birth). These antibodies help to protect the kittens against infection until their immune system is more mature, and they usually last around six to 10 weeks. High levels of these maternal antibodies will interfere with the vaccine's ability to stimulate a proper immune response from the kitten. A booster vaccination given one year later may enhance the initial vaccine response, especially when immunisation might have been less than optimal due to maternal antibodies.
Both lack of efficacy and adverse reactions are sometimes reported following vaccination. Such problems are rare and seldom serious, and the benefits of vaccination far outweigh the small risk of an adverse reaction occurring. However, adverse reactions at times can be severe and are therefore a cause for some concern. Mild and self-limiting reactions such as pain or swelling at the injection site, and mild malaise for a short period are not unusual. Indeed, as the purpose of vaccination is to provoke an immune response in the cat, it is inevitable that such reactions will occasionally occur.
In the UK, a Suspected Adverse Reactions (SAR) Surveillance Scheme (SARSS) is run by the Veterinary Medicines Directorate (VMD) for licensed veterinary medicines. Most SARs are reported voluntarily by veterinary surgeons or members of the public when an adverse reaction is suspected following the use and/or administration of a licensed veterinary product (including vaccines). Because this is a ‘passive' or voluntary reporting scheme, it is inevitable that not all adverse reactions will be reported to the VMD and this probably applies particularly to less serious adverse effects. During the period from 1995-1999, there were 2158 SARs reported to the VMD in cats, and of these 835 (39 per cent) were associated with the use of vaccines. Not all SARs are genuinely adverse reactions to the product being used, and causality can be difficult to establish. Nevertheless, even if all the SARs associated with feline vaccines were genuinely as a result of vaccination, this still represents a very low rate of SARs of about 0.61 per 10,000 doses of vaccine sold. Nearly 50 per cent of SARs to vaccination occur in cats less than 6 months of age (ie, in relation to their primary vaccination course).
Some of the SARs reported following vaccinations in cats (along with their approximate frequency during the period 1995-1999) are:
Lameness/polyarthritis – 18%
Local injection site reactions – 16%
Allergic reactions (anaphylaxis and hypersensitivity) – 9 %
Lack of efficacy – 6%
Upper respiratory tract disease – 6%
Sarcomas – 3%
There is some evidence for a small increase in the incidence of vaccine SARs, but this is difficult to assess as it may be that veterinary surgeons are becoming more vigilant in reporting SARs to the VMD. There is also some evidence that certain vaccines are more likely to produce SARs than others although again, data are limited.
The Cat Group recognises that adverse reactions do occur following the use of vaccines, and further that due to the passive nature of the reporting scheme, the current estimate of SARs based on the SARSS will be an underestimate of the true incidence. Nevertheless, current data demonstrate that adverse reactions are uncommon, and are usually mild and self-limiting in nature.
Severe adverse reactions do occur sometimes, and vaccinesite or injection-site sarcomas (tumours) have been reported in the UK as well as elsewhere. These tumours are aggressive and difficult to manage. In the USA vaccine-site sarcomas have been recognised for a number of years and are thought to occur with a frequency of approximately 1 per 10,000 doses of vaccine administered. Some studies have suggested that rabies vaccines (which are mandatory in the USA ) may be one of the vaccines more likely to be associated with these sarcomas. Since rabies vaccination is not routine in the UK , this may be one reason why these tumours appear to be seen less commonly in the UK than the USA . Such severe reactions are undoubtedly very rare, even in the USA , and the benefits of vaccination clearly outweigh the risks involved. Nevertheless, the risks associated with vaccination should be weighed alongside the benefits in all cats when determining with the owner the type and frequency of vaccination that is most appropriate.
The Cat Group encourage reporting of SARs to the VMD, ideally through the veterinary surgeon involved who can provide valuable additional information. The address of the VMD is:
Veterinary Medicines Directorate
Freepost KT 4503
Surrey KT15 3BR
In addition to the VMD, any SAR can also be reported to the vaccine manufacturer ‘Yellow Forms' (MLA252A) are supplied by the VMD to veterinary surgeons specifically for this purpose and are available from the VMD web site: www.vmd.gov.uk . The Cat Group would also encourage the development of an active prospective scheme for identifying and classifying SARs associated with vaccination and thus defining their true incidence.
The necessity to vaccinate all cats against all the diseases for which vaccines are available has been challenged. The life-style and environment in which some cats are kept means they may not be at risk of exposure to certain diseases. For example, a cat that is kept strictly indoors and is in single cat household has no appreciable risk of exposure to Chlamydophila felis or FeLV infection, as these organisms generally require direct contact between cats for transmission to occur. As vaccination cannot be regarded as an entirely innocuous procedure it may therefore not always be appropriate to use certain vaccines. The American Association of Feline Practitioners has recently suggested considering feline vaccines as either ‘core' or ‘non-core'. Core vaccines would be those whose routine use can be justified in all cats based on the prevalence of infection, the possibility of indirect transmission (ie, not just through direct cat to cat contact) and the severity of disease. ‘Non-core' vaccines would be other vaccines that are potentially very valuable in certain situations where cats are at genuine risk of exposure to the organism, but whose use is difficult to justify in all cats.
The Cat Group supports the discriminatory use of feline vaccines in the UK . Feline infectious enteritis, feline herpesvirus- 1 and feline calicivirus should be regarded as essential (or ‘core') vaccines in the UK , and the Cat Group recommends vaccination of all cats against these viruses. The parvovirus which causes feline infectious enteritis is a very resistant virus (thus indirect transmission of the virus is common) and subsequent disease can be fatal. Both FCV and FHV-1 are very prevalent viruses and although probably mainly transmitted by direct or close contact, these viruses can survive in the environment and indirect transmission is therefore possible. For these reasons the Cat Group recommend routine use of these vaccines. The use of other vaccines cannot necessarily be justified in all circumstances and the Cat Group recommends the use of these vaccines be determined on a case-by-case basis according to individual needs.
The Cat Group therefore supports the 2002 report of the Veterinary Products Committee Working Group on Feline and Canine Vaccination where a recommendation was made that manufacturers market single component as well as multivalent (combined) products in order to maintain flexibility over their use.
Immunity following initial vaccination may not be life-long, and booster vaccinations are recommended to maintain good vaccineinduced protection. For most vaccines, manufacturers recommend administration of annual boosters (injections) to maintain the immune response. This recommendation has been adopted for a variety of reasons including the desire to ensure that pets are properly protected from disease where possible and the uncertainty (and likely variability between individual cats, between different diseases and between different vaccines) about how long vaccine-induced immunity will last. Additionally boarding catteries frequently require an ‘up to date' vaccination certificate prior to accepting boarders (ie, proof of vaccination within the preceding 12 months).
The 2002 report of the Veterinary Products Committee Working Group on Feline and Canine Vaccination recommended that ‘‘statements be added to the product literature indicating that the regime for booster vaccinations is based on minimum duration of immunity rather than maximum' and that ‘a risk/benefit assessment should be made for each individual animal …so that …an informed choice can be made by the owner with respect to the necessity for a particular vaccine and the frequency of its use'. However the Working Group also concluded that ‘there is insufficient information to propose re-vaccination intervals on product literature other than those recommended by the manufacturer'.
Nevertheless, there are recent studies that have suggested that vaccine-induced immunity for some diseases may last considerably longer than 12 months. This, and other evidence, led to an Advisory Panel Report from the American Association of Feline Practitioners and the American Academy of Feline Medicine on the use of feline vaccines in 1998, with some revisions in 2000. This report recommended that based on current evidence, in general following a first annual booster vaccination, cats should be vaccinated no more frequently than every three years for feline infectious enteritis, and in general every three years for FCV and FHV-1. For other diseases where insufficient evidence existed they recommended annual vaccination. However, they also recommended that ‘vaccination needs of adult cats should be assessed at least once yearly, and if necessary, modified on the basis of an assessment of their risk'.
The Cat Group recognises that there is genuine difference of opinion among clinicians and scientists at present on the necessary frequency of booster vaccination for adult cats. Furthermore, at present there are insufficient data available to determine optimum booster intervals in adult cats. The Cat Group encourages informed consent of owners for vaccination of their cats wherein both the risks and benefits of vaccination as well as the need for vaccination are discussed with owners and advice is provided on the basis of the best available objective data. The Cat Group also supports and encourages further studies to determine the maximum duration of immunity in vaccinated cats to provide additional evidence for future vaccine booster interval recommendations.
It has been suggested that serological testing (looking for the quantity of antibodies present in a blood sample) may be used instead of routine booster vaccinations to assess the need for vaccination. The assumption here is that a booster vaccine would be unnecessary unless antibody concentrations had fallen below a critical level considered to be protective. However, with the exception of parvovirus (feline infectious enteritis) and rabies, there is not a good correlation between antibody concentrations in the blood and protection against disease, and tests for antibody concentrations are not standardised between laboratories. For these reasons the Cat Group urge caution in the use and interpretation of serological testing in cats and do not believe there is sufficient data to recommend this in lieu of vaccination.
Coyne MJ, et al (2001) Duration of immunity in cats after vaccination or naturally acquired infection. Veterinary Record 149 545-8.
Elston T et al (1998) 1998 report of the American Association of Feline Practitioners and Academy of Feline Medicine Advisory Panel on Feline Vaccines. Journal of the American Veterinary Medical Association 212 227-41
Gaskell RM, Gettinby G, Graham SJ, Skilton D (2002) Veterinary Products Committee (VPC) Working Group on Feline and Canine Vaccination – Final Report to the VPC. Department for Environment, Food & Rural Affairs, PB 6432. www.vpc.gov.uk
Kruth SA, Ellis JA (1998) Vaccination of dogs and cats: general principles and duration of immunity. Canadian Veterinary Journal 39 423-6
Lappin MR, Andrews J, Jensen WA (2002) Use of serologic tests to predict resistance to feline herpesvirus-1, feline calicivirus, and feline parvovirus infection in cats. Journal of the American Veterinary Medical Association 219 38-42
McEntee MC, Page RL (2001) Feline vaccine-associated sarcomas. Journal of Veterinary Internal Medicine 15 176-82
Meyer EK (2001) Vaccine-associated adverse events. Veterinary Clinics of North America - Small Animal Practice 31 493-514
Richards J, et al (2001) 2000 Report of the American Association of Feline Practitioners and Academy of Feline Medicine Advisory Panel on Feline Vaccines. Journal of Feline Medicine and Surgery 3 47-72
Scott FW, Geissinger CM (1999) Long-term immunity in cats vaccinated with an inactivated trivalent vaccine. American Journal of Veterinary Research 60 652-8.
Updated May 2006
Indoor cats are still at risk of contracting various infectious diseases. There are some infections that can only be transmitted by direct contact between cats (eg, FeLV) and, if cats are kept on their own indoors, there may therefore be no appreciable risk of encountering some diseases (and thus vaccination may not be necessary). However, some other infectious agents are extremely common and can survive for variable periods outside of the cat, and can therefore be transmitted indirectly (for example transmitted via shoes or clothing). For some infectious agents (such as feline panleucopenia) the risk of transmission in this way is very significant as the virus can accumulate in the environment and can survive for prolonged periods of time. Indoor cats do occasionally escape or have to be taken to a veterinary surgery because they are ill. While veterinary practices will take precautions to minimise the spread of disease, they are obviously a place where sick cats are taken and therefore post a higher risk to unvaccinated cats. The concept of ‘core vaccines' (see the Cat Group Policy Statement) is equally applicable to indoor and outdoor cats – core vaccines are those that should be used in all cats regardless of their circumstances.
There has been some speculation in the past that certain cat breeds may be more susceptible to adverse reactions following the use of certain vaccines. However, at this stage, there is no substantial evidence at all that certain breeds are more (or less) likely to suffer adverse vaccine reactions than others.
Older cats can be affected by infectious diseases just as younger cats can. The Cat Group encourages the application of good scientific knowledge and the best current scientific opinion in trying to determine how frequently cats should be vaccinated. However, there is no evidence at present, given that vaccine-induced immunity is generally not life-long, that there is an age beyond which vaccination should not be considered. Even older cats may still benefit substantially from vaccination, and as with any cat, the range and frequency of vaccination should be considered on an individual basis bearing in mind genuine risks and needs.
Cats infected with FeLV and FIV often suffer progressive damage to their immune system caused by these viral infections. However, in most cats, during the majority of their infections, this will not prevent them responding to vaccines, and so long as they remain relatively healthy, routine vaccination is still recommended. There is some evidence that the use of killed rather than live vaccines may be preferable though in these situations.
Current evidence indicates these are very rare side-effects following vaccination, and are probably less common in the UK than in the USA . There is some evidence that sarcomas may occasionally arise following the use of other injectable products as well, and some have now referred to this syndrome as ‘feline injection-site sarcomas' or FISS.
There has been a recommendation made by certain veterinary groups in the USA for a number of years now, that different vaccine components be injected in different sites in cats. Specifically the recommendation has been to inject rabies vaccines in the right hind leg, leukaemia virus vaccines in the left hind leg, and remaining injectable vaccines in the usual site (the ‘scruff'). The reason for these recommendations was two-fold: Firstly, that if rabies and/or feline leukaemia virus vaccines were a more common cause of injection site sarcomas, leg amputation may offer a life-saving option for treatment. Secondly, these recommendations were devised so that over time it would be possible to determine if specific vaccines were indeed responsible for the development of injection-site sarcomas.
The most recent publications from the USA on the problem of vaccine-associated sarcomas have highlighted a number of issues. It is still not yet clear whether or not the use of leukaemia virus vaccines and rabies virus vaccines are more likely to induce injection-site sarcomas than other vaccines – current evidence on this is controversial. Recent studies have not found any difference in the likelihood of injections site sarcomas comparing products from many different vaccine manufacturers (with no difference between adjuvanted and non-adjuvanted products). Several studies have now identified injection site sarcoma development following administration of other (non-vaccine) injectable products to cats. The true incidence of injection site sarcomas appears to be considerably lower than some of the earlier estimates, and although devastating for the individual cat affected, the frequency of this adverse reaction needs to be kept in perspective.
The recent developments suggest that vaccination itself is not sufficient to cause development of a sarcoma, but rather this occurs in some cats perhaps as a result of a genetic predisposition to develop sarcomas following inflammatory change in soft tissues (such as can be induced by vaccination, other injections, or other forms of trauma).
Because of the complexity of the situation, the infrequency of injection site sarcomas, and the impossibility of knowing what is currently most important in the development of the tumours in cats in both the UK and the USA , it is extremely hard to make definitive recommendations over the sites where vaccines should be administered.
Making a strong link with FeLV vaccines is potentially dangerous at this stage, and singling out administration of these vaccines in a rear leg may not necessarily be advisable based on current evidence. Furthermore, current estimates of the incidence of VAS in North America have suggested a frequency that may be as low as 1:10,000-30,000 doses.
The Cat Group strongly encourages judicious use of vaccines based on the real need for protection of an individual cat, while weighing up the risks and benefits from the use of any particular vaccine. Where there is particular concern over the possibility of an injection-site sarcoma occurring, it would be feasible to provide an option to inject the vaccine (all components, not just FeLV) in a rear leg - this has been recommended both to enable a clearer understanding of the relationship between different injections and the development of sarcomas, and also because sarcomas developing in the limbs may be easier to treat. However, studies specifically looking at the efficacy of this recommendation have not been published.
Any environment where large numbers of cats are housed and cared for has potential for the spread of disease. Therefore, any cat (of any age) going into a cattery should have good protection. Not all catteries have the same excellent standards of construction and management (particularly relating to hygiene) as those which have been inspected and Listed by FAB. The risks at poor catteries could be very high indeed. See www.icatcare.org for more information.