April 27 2006 ~ Freedom of Information query produces very little to support Mr Bradshaw's assertion about vaccination
Under the FOI Act, a request was made for a list of the references which led the Minister and his officials to assert that "It has been a frequently recognised feature of the use of vaccine in the field that vaccinated birds can continue to allow spread of the virus, whilst not showing typical clinical signs." (see also below) While it may perhaps have been true that, in the past, it was often assumed that vaccinates could excrete small amounts of virus, and if infected before vaccination, be infected without clinical signs, it is nevertheless quite misleading to imply that therefore there are good veterinary reasons not to vaccinate.
To cite the recent paper by Ellis et al ‘Vaccination of chickens against H5N1 avian influenza in the face of an outbreak interrupts virus transmission’ Avian Pathology, 2004, 33(4):405–412. as one reference that was supposed to support the Government's assertion, is astounding. In fact, the paper says
"after 18 days post-vaccination no more deaths from H5N1 avian influenza occurred and intensive monitoring by virus culture on these farms showed no evidence of asymptomatic shedding of the virus.."Even if it were true that vaccinates could, if infected before vaccination, excrete small amounts of virus, this will not affect other vaccinated birds - and vaccination is carried out on ALL birds on a holding. We should be grateful for informed comments about the the information given by FOI
from Jim Hungerford, General Manager of Intervet UK
I've attached the press release and Q&A's that we have sent out here in the UK about vaccination.
As it says, our position is that zoo and free range birds should receive preventative vaccination. Our reasoning is that these are the birds most at risk and they are solidly protected for 12 months after the two doses of vaccine - if they are exposed to any virus it will not become established or be transmitted (as exposure is an unpredictable risk with migrating waterfowl, we believe vaccination should start now to ensure these birds are protected as soon as possible). The use of non-vaccinated sentinel birds and antibody (DIVA) testing provides the appropriate assurance of vaccination, non-exposure and non-infection. The government proposal of waiting for an outbreak will require slaughter of the exposed birds (clearly unacceptable in a zoo situation) and the emergency vaccination and quarantine in the surrounding zone. If despite this the infection spread, I can't see society accepting a repeat of the terrible scenes that we saw during the FMD crisis, and I hate to think what it would do to our agriculture. Also, the proposal to house free range birds for months in buildings that are only designed for overnight use poses major animal welfare problems. Finally, emergency vaccination (with a single dose) is never as good as the full course of two doses.
You can see why we are supporting preventative vaccination of these birds! Unfortunately, as with FMD, the anti-vaccination message seems to be the official line, but we are doing what we can to provide people with the other side of the argument.
I hope the above is helpful, please say if you would like anything more.
Further email recieved March 2 2006 from Jim Hungerford, General Manager of Intervet UK
To my understanding, there are no 'silent carriers'. When our vaccine is used as recommended (2 doses 4-6 weeks) apart it prevents transmission of the disease, even with the high challenges used experimentally. The reason for this is that the very few birds that do get infected from the experimental challenge shed extremely small amounts of virus - 10,000 to 100,000 times less - and that these minute amounts of virus are too small to infect other birds. The infection then dies out - no new birds get infected, and the few infected birds (which are not clinically sick) recover and clear themselves of the infection.
I think the differences are between what is measurable (in any field you can typically find something out of the ordinary if you look with extremely sensitive techniques), versus what is significant in the real world. The demonstration of this is what happened in Hong Kong during their outbreak - vaccination, as part of a very stringent overall control program, stopped virus circulation on infected premises from 18 days after the vaccination started. Importantly, carriers were not found. These findings are reported in the attached publication. ( "Vaccination of chickens against H5N1 avian in?uenza in the face of an outbreak interrupts virus transmission" Avian Pathology (August 2004) 33(4), 405 /412 )
Revised: 1 March 2006
Poultry vaccination is vital to control avian flu
As the UK government takes precautionary measures and places an order for over 2 million doses of Nobilis Influenza, the only vaccine licensed in the UK to protect birds against the H5N1 avian flu strain, Intervet UK sets out the argument for vaccines. General Manager of Intervet UK, Jim Hungerford, answers some of the topical questions.
1. Why do you have a vaccine for the H5N2 strain of avian flu when it is the H5N1 strain that is causing the problem?
Intervet produces a H5N2 vaccine, which is closely related to the present H5N1 strain so that it induces protection, but also allows differentiation of vaccinated versus infected birds.
2. How quickly will the birds be protected after vaccination?
Birds have to build up immunity following vaccination. We have indications that the protection starts 1-2 weeks post vaccination. After 3 weeks, there is significant protection that peaks at approximately 5 weeks after vaccination. The duration of protection is increased to one year by re-vaccinating 4-6 weeks after the first vaccination.
The first injection will provide protection against clinical disease from at least 2 weeks onwards and reduce excretion of virus dramatically. As a result, it will reduce the spread of disease and, for the few birds that do get infected the amount of virus produced will be drastically reduced.
3. Are there any vaccination methods other than injection?
The vaccines currently used are inactivated vaccines, which means that the virus is inactivated (not live) and in order to get a good immune response the vaccine has to be injected. Intervet is investigating the possibilities for mass application, which could be for example spray or water application. However, this does require developing a new type of vaccine, e.g. by applying biotech methods. Research projects are in an early stage and it will take time before such a product can be registered and then brought to the market.
4. How can vaccinated animals be differentiated from infected animals?
Intervet’s vaccine is based on a different strain (H5N2) than the current field strain (H5N1). Because the vaccine is based on a H5 strain it fully protects against all H5 viruses. If you vaccinate with H5N2 you get extra antibodies in the vaccinated animals (against the N2) that you don’t get if birds get infected with H5N1. You can monitor these antibodies with a number of standard methods.
5. Does the vaccination mask field infection?
No. Vaccinated chickens may rarely still become infected. A minority of these few chickens may still excrete a very limited amount of virus. However, the amount of virus is too small to infect other birds. The excretion is so limited that it does not lead to the transmission of the virus.
In Hong Kong, Intervet’s vaccine has been used extensively on infected farms. On these farms virus transmission was blocked completely from 18 days after vaccination. Vaccinated birds no longer transmitted the virus and did not turn into carriers.
Further information is available on our dedicated website http://www.avian-influenza.com/
6. How is avian flu transmitted from bird to bird and from birds to humans?
Infected birds excrete high amounts of virus in their droppings, which facilitates further spread. Bird to bird infection mainly occurs by inhaling the virus whilst breathing. From poultry house to poultry house the virus is transmitted mainly by contact with contaminated equipment and/or movement of birds and people. People can be become sick when they are exposed to a large amount of virus caused by intensive contact with infected birds.
7. Is it safe to eat birds vaccinated with inactivated AI vaccine?
Yes, it is perfectly safe. To keep birds healthy, all of our commercial British poultry are vaccinated routinely against various diseases, so of course poultry products from those vaccinated birds are safe for consumption. This is the same for birds vaccinated with Nobilis Influenza. The withdrawal period for the vaccine is zero days. (The withdrawal period is the time which passes between the last dose of a medicine given to the animal and the time when it can be used for human consumption).
Therefore, it is both safe and effective for poultry to be vaccinated and safe for people to eat birds that have been vaccinated. There is also no risk associated with eating eggs from vaccinated hens. It is important to emphasise that avian flu cannot be passed on by eating poultry or eggs.
Statement from an independent third party
The Netherlands Nutrition Centre (Voedingscentrum) states that eating prepared chicken meat and eggs is safe even when avian flu is prevalent. This also applies when it comes from chickens which have been vaccinated against avian influenza. The virus can only infect people who have intensive contact with sick or dead birds.
Moreover, the Government will make every effort to ensure the virus is not present in chickens and eggs that are sold. This will not only protect the consumer but will also prevent the spread of the disease. In the hypothetical event that infected chicken meat or eggs would be sold the virus will not survive cooking.
8. Do you make vaccines for avian flu regularly?
Yes, we produce vaccines on a regular basis to protect birds against Avian Influenza caused by different strains occurring more frequently such as H9, H5, H7.
9. How much vaccine do you have available? How quickly can you supply? Is it enough for the countries affected now?
We produce the vaccine in question on a regular basis. We have sufficient stock to support our regular sales. In case of a sudden substantial increase in demand we still can increase our production. However, delivery can vary from a few weeks to some months. This depends on the stage of the production process, orders that have been placed and our current stock situation. We can only supply if we receive official orders. We cannot guarantee immediate supply if demand is growing.
Britain’s first shipment of Nobilis Influenza vaccine will arrive by mid March.
10. How long does it take to make new batches of vaccines?
It normally takes months to start from the suitable antigen in stock before you have produced a batch and you then have to run all required quality control tests. Even if you speed up production as much as possible, it will still take several weeks to get a batch produced ready for tests.
Testing of the vaccine has to be done according to European Regulations on antigen and final product. In case of an emergency, testing of the final product can (partially) be waived with approval of the UK authority, and if so the product may become available earlier.
11. Where is your avian flu vaccine made? Intervet routinely produces AI vaccines in Spain and Mexico.
12. How are the birds actually vaccinated?
Birds are vaccinated by injection under the skin or into the muscle.
13. How much does it cost to vaccinate?
The vaccine costs around three pence per dose, which equates to six pence per bird, as they need two doses. There are also associated labour costs for administering the vaccine.
14. What is your recommendation regarding vaccination?
Intervet is recommending that the UK’s free range hens (approximately 9 million) and other outdoor birds are vaccinated to help in the fight to keep avian flu out of the UK’s poultry flock.
15. Wouldn’t it be cheaper just to move the free range hens indoors?
While this is a good theoretical solution, we believe that it would be impossible to achieve in reality without serious welfare implications. Some free range farmers will not have the facilities to do this and hens that are not used to being kept in close proximity have a tendency to fight. A pro-active vaccination policy will also help avoid the need for millions of birds to be destroyed should an outbreak occur.
16. Germany has reported a suspected case of a cat infected with bird flu
strain H5N1. Can cats be vaccinated against bird flu? Do you have a
During the 2003 to 2004 outbreak of avian influenza A (H5N1) virus in Asia,
fatal infection in domestic cats was reported. Studies at independent
institutes* have also shown that domestic cats are at risk of disease or death
from the H5N1 virus and therefore it has been advised that cats in infected
areas should be kept away from contact with wild birds or domestic poultry.
As Avian Influenza has not been found in the UK we do not recommend that
owners of domestic cats take any new precautions.
Intervet does not currently have a vaccine available to protect cats against the
H5N1 virus, however preliminary studies have suggested that it may be
possible to develop a suitable vaccine for use in this species.
The Intervet Nobilis influenza vaccine developed to protect birds is not
designed (and not licensed) for use in cats, which are more sensitive to the
*(Rimmelzwaan et al_ 168 (1) 176 - American Journal of Pathology; Kuiken et al Avian H5N1 influenza in cats Science 2004; Brown 168 (1) 6 - American Journal of Pathology)
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23 February 2006
Poultry vaccination is vital to control avian flu
Britain’s first consignment of Nobilis Influenza vaccine – the only vaccine licensed in the UK to protect birds against the H5N1 avian flu strain – will arrive mid March. Over two million doses have been ordered by the Government to be held in reserve as a conservation measure for UK captive rare and endangered species of birds, such as the Tower of London’s iconic ravens.
Intervet, the world’s largest animal vaccine producer, welcomes this week’s European decision to allow specific French and Dutch poultry vaccination. The company also believes that the UK should follow suit and vaccinate the country’s nine million free range hens and other outdoor birds to help in the fight to keep avian flu out of Britain’s avian flocks. This precautionary measure would prevent the terrible scenes that followed the foot & mouth outbreak when over four million animals were destroyed.
“The UK has an excellent standard of animal welfare within the poultry industry but we believe that bringing free range flocks indoors or leaving them unvaccinated will compromise the welfare of the birds, as well as risking the spread of disease. In addition, vaccinating all free range hens is much more cost effective than the compensation that would follow if the flocks were slaughtered,” says Jim Hungerford, General Manager of Intervet UK Ltd.
Nobilis Influenza has been successfully used in avian flu control programmes across the globe. The vaccine is scientifically proven to prevent virus transmission from bird to bird and protects poultry from the clinical effects of the disease. It also massively reduces – by more than 100,000 fold – the amount of virus in exposed poultry, dramatically diminishing the risk of spread to humans and the risk of spread to other poultry.
Intervet has been working with many governments, including the UK government, to advise on outbreak control and management as well as vaccination strategies aimed at helping bring the epidemic to a halt. One such recommendation is for governments to commission a ‘vaccine bank’, whereby they can pre-order vaccine which is then held in stock and can be delivered within three days’ notice. France and Japan have already established vaccine banks.
- ends -
Notes to editor:
1. THE FIRST BOTTLE OF AVIAN FLU VACCINE WILL BE DELIVERED TO THE UK ON FRIDAY 24 FEBRUARY FOR PHOTOGRAPHY PURPOSES.
2. Intervet’s Nobilis Influenza vaccine is suitable for protecting poultry against Avian Influenza type A, subtype H5 and also subtypes H7 and H9. The company’s vaccine has already been used extensively and very successfully in Hong Kong, Italy, Mexico and other areas of the world in official governmental avian ‘flu control programmes and is now being used in France, the Netherlands and Belgium.
3. The sale and supply of Nobilis Influenza vaccines will only be permitted under strict guidelines set out by the European Community legislation on the control of avian influenza. Use of the vaccine is strictly under the control of Defra and the product is categorised as a prescription only veterinary medicine, POM-V.
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