Vaccine Related Issues

To Vet Times, BSAVA, BVA, the Kennel Club, the FAB, and the Dog and Cat Press 5th May 2004.

Re the Recent debates as to whether annual booster vaccination of animals is necessary. We appreciate that the recent developments (1) in the ongoing controversy regarding annual booster vaccines for dogs and cats has left the veterinary profession and the pet owning public in a dilemma as to the direction they should take, especially when considering the animal welfare and consumer protection issues involved. It seems that on one hand you have the vaccine manufacturers, who appear to be hiding behind legislation and the advice of an industry report (2). Their stance that annual vaccination must be continued relies on the following points

(a) They do not know the actual duration of immunity

(b) Vaccines do not cause significant harm, so annual vaccination is acceptable. This is also the stated view of the veterinary organisations i.e. the BVA and BSAVA (3) However, the incoming President of the BSAVA Dr Ian Mason has been reported as saying 'after due consideration of the evidence, the current recommendations on vaccination of animals may need to be refined' (4). Vaccine manufacturers must have known about the changes in recommendations in response to detailed evidence in the US for some time, and have been affiliated to UK groups, such as the Cat Group (11) that have been looking at the work quoted (1). So far it seems the only action to be taken has been that of Intervet UK in extending their duration of immunity for Distemper, Hepatitis and Parvo to 3 years. While this is to be welcomed, no mention has been made yet of the Cat situation. On the other side there is a small but growing number of veterinary surgeons and a strongly supportive public who are citing recent reports and research (5,6,7,17,18) and conclude

(a) That duration of immunity for parvovirus, adenovirus, distemper (5), and feline enteritis (18), is established as 7 years, and for feline calicivirus and herpes (5,18) is established for at least 4 years, and it seems that giving booster vaccinations does not offer any further protection (6).Therefore, annual vaccination is not needed for dogs and cats (with the exception of Leptospirosis, discussed below)

(b) That vaccines can cause harm (5,8,9,11,14,18) and therefore unnecessary vaccination should be avoided if at all possible. Additionally they also consider that information from the manufacturers is notable. These state that about 50% of dogs (10) and 2/3 of cats (10,11) in the UK are not vaccinated at all or only infrequently, but where are the reported outbreaks of the diseases one would expect if the duration of immunity were so short as to need annual Boosters? While following the recent debate, there seems to have been only two arguments put forward for continuing annual booster vaccines in dogs and cats. First there has been suggestion that the originating letter calling for cessation of booster vaccines was written by homeopaths and by inference should be ignored, in fact this was cited as relevant correspondence for the debate in a mailing from a vaccine manufacturer to all vets in the UK (12) and the profession is misguidedly it seems seeking to use this (13). Whilst it is true that some of the signatories have interests in this field, it is certainly not the case that all the signatories do. All are scientifically trained Vets in the first instance, all recommend initial vaccination, and they quote the recent published orthodox research of others. Secondly, and perhaps more significantly, is the argument for Leptospirosis vaccine, where it is claimed there is a poor duration of immunity and so annual vaccination of dogs only for this must continue. This has been the basis of much research in the USA, and it is appropriate that we in the UK are aware of the findings. We summarise them below

1. Immunity to Leptospirosis is complex and poorly understood. It can only be measured by challenge studies. This is ethically unacceptable so we have to examine what is happening in the field by epidemiological methods (5).

2. Kansas University reports that the Leptospirosis vaccine is THE major cause of vaccine reactions, so much so that they consider the risks outweigh the benefits. It is no longer considered a core vaccine and they even recommend it should not be given to puppies (9,14).

3. Another study found the vaccine highly immunosuppressive and recommended that the vaccine should not be given in conjunction with other vaccines (it is currently in the UK).

4. The Leptospirosis vaccine does not protect the dog from being infected with the disease; it just minimises the clinical symptoms. Hence there seems to be/have been a real risk of vaccinated healthy dogs shedding the spirochetes so possibly posing a threat to other dogs and humans. Although one manufacturer has recently claimed it has a new vaccine to prevent this, the clinical study conducted to test the vaccine was based on a sample of only 6 dogs (15). In our opinion a study so narrowly based cannot of course be scientifically credible.

5. The duration of immunity measurable by titre induced by the Leptospirosis vaccine can be as little as a few months (14,16) yet the advised interval for boosters is 1 year, which it seems has been an entirely arbitrary recommendation. By inference it may well be therefore that even vaccinated dogs have not been protected as their owners expect.

6. There is little protection between serovars (types). Use of the vaccine in the USA has led to a shift in the serovars such that the serovars now infecting dogs are not the ones used in the vaccines (14). Can we assume this is true also in the UK? Are we now vaccinating against a disease that barely exists in the form vaccinated for?

7. The vaccine efficacy seems between only 50 -70%, depending on the author (5). The outgoing president of the BSAVA, Dr Freda Scott-Park, stated that when the science is there the profession would respond. The science is here, and the profession must respond now or lose all credibility in this debate. In the USA working parties have resulted in the removal of mass vaccination requirements in favour of individual vaccination programmes and consumer choice. This would answer the issues of insurance and kennels/catteries that are now being raised as well as restoring public faith in the industry. Whilst we have no wish to presuppose findings in the UK, it is our desire to establish a truly independent working party under lay chairmanship critically to review the scientific data, to raise questions with the manufacturers and report as soon as practically possible to the profession and the public.

Our thanks to Sylvia Evans for providing this article