Vaccine protocols under microscope

Vet Times The website for the veterinary profession https://www.vettimes.co.uk Vaccine protocols under microscope Author : ROBIN FEARON Categories : Vets Date : March 24, 2008 ROBIN FEARON finds that controversy over the benefits or harm of animal vaccination continues, and uncovers industry advice on data sheet recommendations IN times when vaccination protocols seem less than constant, stick to the vaccine manufacturers data sheets is the firm message from Fort Dodge technical services manager Mike Davies. Talking at the company s small animal infectious disease CPD days, he maintains it is the rational way to avoid litigation over immunisation practices. Lawsuits did not flow thick and fast following publication of a letter in a January 2004 edition of Veterinary Times (VT 34.02), endorsed by more than 30 veterinary surgeons, pointing out the harm done by modern vaccination regimes. Neither did the profession rest on its laurels following this wake-up call, and support for immunisation has been loud and vocal. But the question was asked: should protocols be reconsidered? Mike s approach is pragmatic and certain. Always stick to the data sheet protocol, is his recommendation. You may be in a dilemma because a lot of advice is contrary to that fact, but if you stick to data sheet information, unless you have a compelling reason not to do so, then manufacturers can stand by you in a litigious situation. Whatever it promises, vaccination is not a guarantee against disease. In some cases it minimises the severity, but it offers the best option for diseases where there is no medical cure. Immunity must be kept at a high enough level to provide individual and herd protection. There are a vast array of vaccine products in the global and UK markets everything from 1 / 15

inactivated to live modified, whole organism to sub-unit or recombinant vaccines. There are univalent and multivalent vaccines too, and that means the protocol varies for each product. Confusion has proliferated because of anti-vaccination groups with veterinary backing, issues about side effects, conflicting expert committee advice, and a general maelstrom of anecdotal claims about immunisation. As a profession, we don t read the data sheets closely, states Mike. I know we do it to find out the dose rates, but unless you read them regularly you won t have noticed the amount of changes over the past three or four years. Every single recognised side effect is listed now. Every single statement has been proved to the regulatory authorities. If we wanted to change a vaccine protocol because of expert panel opinion, even if a company obtains that data, there is a time lag between that and changes in the product licence. I am simply not allowed to recommend off-licence use of a Fort Dodge vaccine. That is not to say that different countries and licensing regimes do not have an influence. If you go to America or Australia, products with the same name an content can have totally different data sheet recommendations. In the UK, some products are licensed by the VMD and some have paneuropean approval. Arguments for re-evaluation of vaccine protocols tend to centre on frequency of administration and the duration of immunity. However, Mike simply believes that safety and efficacy lead the argument. Every company with a vaccine on the market has to undergo rigorous safety testing on the target species and the users of the vaccines, as well as with regard to the environment, he says. We don t measure efficacy by antibodies in the bloodstream. The only way to demonstrate that the vaccine works is to have groups of vaccinated and non-vaccinated animals, then to challenge both with real, live infectious agents. Anybody can stand up and say that they don t think it works well enough. That may be their point of view, but scientific evidence shows it benefits a significant number of animals. Search for answers Even a cursory internet search on the dangers of canine or feline vaccination throws up thousands of references. Many websites include statements from veterinary surgeons describing illness from routine vaccination or vaccinosis. Despite the weight of evidence for vaccine safety, these sources have a negative impact on public opinion, says Mike. He explains: The basic premise is that vaccinations cause more harm than good. Clients or breeders believe these websites, even if they are not true, because there is veterinary weight behind it. They question the true duration of 2 / 15

immunity, which vaccines are suitable for each breed, are they necessary and should they be given at all. The infamous Veterinary Times letter mentioned which was signed by 31 registered vets was a coup for those opposed to routine annual vaccination. It culled evidence from journals including the Journal of the American Veterinary Medical Association, but Mike refutes statements included in the letter. They say that the immune systems of dogs and cats mature fully at six months and any modified live vaccine given after that age is good for the life of that pet, he recounts. It is totally untrue and was known to be untrue in 2004. A paper in The Veterinary Record examined dogs previously vaccinated with a modified live distemper vaccine. Out of 144 dogs, 30 per cent did not have protective levels of immunity against the disease, negating lifelong immunity in all cases. Another statement that Mike says is untrue details the fact that if another modified live vaccine is given one year later, antibodies from the first vaccine neutralise those antigens so there is little or no effect. The pet is not boosted and the effect from memory cells is not induced. He says independent data shows that canine adenovirus titres are increased in dogs given a booster injection. Fort Dodge will publish its own study findings on long-term immunity at this year s BSAVA Congress, no doubt stimulating more debate. This whole discussion highlights the true risks and benefits of vaccination and how that should be presented to the public, says Mike. What he finds harder to understand is off-licence recommendations from expert committees on vaccination, specifically the WSAVA Vaccine Guidelines Group (VGG), the European Advisory Board on Cat Diseases (ABCD) and the American Association of Feline Practitioners (AAFP). US guidelines for vaccination classify vaccines into core and non-core categories. Core includes parvovirus, distemper, adenovirus and rabies. All other diseases are non-core, including leptospirosis, parainfluenza, canine coronavirus, Bordetella infection and Lyme disease. Straight away there is a problem because leptospirosis is a real threat in the UK, states Mike. It would be foolhardy for anyone to recommend it as a non-core vaccination. Some WSAVA recommendations, printed last year, were not consistent with any product licences. It recommends that the last vaccination should be given at 16 weeks, and there is no manufacturer that would agree. If you believe in early socialisation, already this conflicts with the idea that you should finish vaccination early. It also says: Booster vaccination need not be done more frequently than every three years after the first annual. What companies have done is demonstrate that for the big three distemper, 3 / 15

adenovirus and parvo vaccination infers sufficient protection for that three-year period. Actually, we endorse annual boosters because there is no evidence it is a problem to do so. In another recommendation, the WSAVA states that in the absence of maternally derived antibodies, a modified live vaccine can provide protection as early as three days after parvovirus, five days after adenovirus, and immediately after distemper virus vaccination. First of all, you must measure whether the puppy has any MDA, says Mike. More seriously, I don t think there are any manufacturers that would tell you a vaccine provides immediate protection in any circumstance. Feline advice Feline recommendations are just as vexing to Mike. Using US definitions, the core vaccines are panleukopaenia, herpes virus, calicivirus and rabies; non-core include feline leukaemia, FIV, Chlamydophila felis and Bordetella bronchiseptica. For the core vaccines panleukopaenia, herpes and calicivirus, the WSAVA says kittens should be given a minimum of three doses, the ABCD recommends a minimum of two, and the AAFP does not specify a number, telling practitioners to begin as early as three weeks, then every three to four weeks until 16 weeks. All offer different advice and, according to Mike, all the advice is offlicence. For feline panleukopaenia, all of them say booster vaccine intervals should be no more frequent than every three years, or longer, he adds. This implies that you should give boosters at three years or longer. In the UK that is simply not a vaccine recommendation. The ABCD group also suggests that in adult cats with unknown vaccination status that a single modified live panleukopenia injection, followed by at least a vaccination at one year, is sufficient for life. That is certainly not approved and to make a lot of these recommendations without data on safety or efficacy is amazing to me. Marian Horzinek is chairman of both the ABCD and the WSAVA VGG. He says the classification of vaccinal antigens as core and non-core was adopted by the WSAVA in 2007 and will be recommended to all national veterinary societies worldwide. The recent changes to revaccination intervals, as reflected in the industry s data sheets, are, in fact, updates following public pressure and expert opinion, he maintains. The ABCD is an industry-independent though Merial-sponsored expert committee and will continue to analyse data published in the scientific literature and make recommendations based on the best available knowledge. 4 / 15

He adds: It is very probable that fewer revaccinations of adult animals with core components will become customary in the UK. This does not apply to non-core vaccines. On the other hand, more animals of any local dog and cat population need to be immunised in order to increase the level of herd immunity and prevent epidemic outbreaks. Mike Davies agrees that minimising the vaccinations we give to pets is a sound principle. The trick is to conduct protocol reviews after a proper risk-benefit analysis based on scientific evidence, not on anecdotal testimony or scaremongering. We don t want to give pets a higher dose or more frequently than we have to, but where do we draw the line? he asks. Should we make boosters once every three years as some experts advise, or maybe every seven years? Industry switch Mike adds: The industry has already switched to three years for parvovirus, distemper and adenovirus, but the others cannot be done. Protection is not good enough for that period in most feline respiratory viruses, and coronavirus vaccine only protects for one year, as do leptospirosis and parainfluenza virus. Data on side effects shows that most products bare up well under scrutiny. Part of Mike s job at Fort Dodge is to compile pharmacovigilance reports on adverse reactions. The VMD and industry then work closely to track changing side-effect trends and can remove products from the market if they prove to be unsafe or inefficacious, though it rarely happens. Most vaccine side effects are transient and mild, but there will always be animals that are immunocompromised in some way, says Mike. How does the profession recognise these pets if they do not present with clinical illness? It cannot, unfortunately. If you talk about a random event, a random death or a serious disease outbreak, one in 365 will occur on the day that you vaccinate an animal; one in 52 will occur within a week, one in 28 will be within two weeks of an animal being vaccinated; and one in 12 will be within a month, he says. When there is a temporal relationship between this event and a vaccination, it still does not mean it is anything to do with the vaccine. Studying facts In a study presented by Mike, data collected from 360 Banfield veterinary hospitals across the US gives a clearer picture of adverse reactions. Based on events reported within three days of the injection, more than 1.2 million dogs were given 3.4 million doses of Fort Dodge vaccine, and out of that number 4,678 reported suspected adverse reactions (0.38 per cent). 5 / 15

Risk factors for reaction susceptibility included the number of antigens administered, age (pets between one and three years old were more likely to react than puppies) and bodyweight (smaller dogs). Signs of a reaction included facial oedema, pruritus and skin changes, hair loss, vomiting (10 per cent), and systemic signs of fever, lethargy or anorexia in five per cent of cases. There was one case of collapse and no deaths. Another study published in JAVMA in 2007 looked at feline cases over a three-year period. Approximately 2,500 cats had a suspect reaction in the 30 days following vaccination, out of nearly 500,000 cats and 1.2million vaccine doses. All vaccines were Fort Dodge except FIP. In this study there were four deaths within 48 hours, but it is not sure if they are due to the vaccine or not, explains Mike. Lethargy, with or without fever is a common symptom, but as vets we advise clients that after a vaccine the cat may be sleepy for a day or two. Local hair loss, vomiting and facial oedema were also recorded. He adds: Multivalent vaccines containing more antigens are associated with an increased risk of side effects, lethargy or fever. Statistically, if you give one antigen the risk is low if you give five together then the risk is increased three times. Knowing the risk factors is one thing, but altering vaccine protocols requires careful consideration, concludes Mike. Much is changing in vaccinology and while science might not have all the answers, his message would appear to be that it still has the best available evidence. Expert panels recommend IF you follow core and non-core recommendations, when is the best time to vaccinate against a non-core potentially fatal disease like leptospirosis, or possibly canine coronavirus? asks Mike Davies. Is it when the local population is unprotected and disease is at a low prevalence? Or is it when the local population is unprotected and there is an outbreak of a virulent form of the disease? Ultimately, vets must assess whether the risk of vaccinating is worse than the disease. Expert panel reports are available on the internet and you can download them with ease. According to Mike there are some fine recommendations, but there is confusion as advice varies between committees. There are also country differences, between the UK, US and Australia, for example. 6 / 15

WSAVA Vaccination Guideline Group (VGG) The VGG was convened to develop global guidelines for the vaccination of dogs and cats, while recognising that the keeping of small pet animals is subject to significant variation in practice and associated economics throughout the world. Despite this, it strongly recommends that, wherever possible, all dogs and cats receive vaccination (www.wsava.org/sac.htm). European Advisory Board on Cat Diseases The ABCD aims to issue guidelines (www.abcd-vets.org/guidelines/index.asp) on the prevention and management of feline infectious disease in Europe, for the benefit of the health and welfare of cats. It says guidelines are based on current scientific knowledge of the diseases and available vaccines. 7 / 15

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Above: microscopic view of parvovirus particles and (right) the molecular structure. It is a fatal disease in dogs, but manufacturers have changed protocols to accommodate a longer duration of immunity on parvovirus vaccines. 9 / 15

Above: microscopic view of parvovirus particles and (right) the molecular structure. It is a fatal disease in dogs, but manufacturers have changed protocols to accommodate a longer duration of immunity on parvovirus vaccines. 10 / 15

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Anybody can stand up and say that they don t think vaccines work well enough. That may their point of view, but scientific evidence shows it benefits a significant number of animals. Mike Davies. 13 / 15

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It is very probable that fewer vaccinations of adult animals with core components will become customary in the UK. This does not apply to non-core vaccines. Marian Horzinek. 15 / 15 Powered by TCPDF (www.tcpdf.org)