Q&A About Bird Flu Vaccine For Poultry

Main Category: Bird Flu / Avian Flu
Also Included In: Veterinary
Article Date: 17 Mar 2006 - 0:00 PDT

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As the UK Government takes precautionary measures and places an order for over 2 million doses of Nobilis Influenza, the 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.

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.

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 6-10 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.

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.

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.

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 vaccinated 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

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.

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.

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.

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.

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.

Where is your avian flu vaccine made?

Intervet routinely produces AI vaccines in Spain and Mexico.

How are the birds actually vaccinated?

Birds are vaccinated by injection under the skin or into the muscle.

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.

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.

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.

What protocol has the Dutch Government adopted with regards to vaccination?

The Dutch Government is already vaccinating zoo birds and endangered species. It has also developed a programme for its free range poultry flocks, incorporating elements of planned vaccination, response assessment and sentinel birds. Intervet believes this type of integrated programme is critical to the successful use of the vaccine.

The aim of the Dutch vaccination programme is to reduce the risk to AI by protecting free range and hobby poultry. Vaccination is at the producer's cost, with the Government paying for the diagnostics.

What about the French Government's prevention plan?

The French Government has implemented a vaccination programme to protect target species like geese and ducks which are kept for rearing. The programme applies to breeding farms located in 373 communities throughout in the regions of Landes, Loire and Vendée.

At present, the vaccination protocol relates only to the geese and duck farms where confinement is not feasible.

http://www.intervet.com

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