2 2006 from Jim Hungerford, General Manager of Intervet UK
Revised: 1 March
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
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.
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.
there any vaccination methods other than injection?
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.
can vaccinated animals be differentiated from infected
Intervetís 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 donít
get if birds get infected with H5N1. You can monitor these antibodies with a
number of standard methods.
5. Does the vaccination mask field
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, Intervetís 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.
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
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
7. Is it safe to eat birds vaccinated with inactivated AI
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.
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.
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.
Britainís 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.
is your avian flu vaccine made? Intervet routinely produces AI vaccines in Spain
12. How are the birds actually vaccinated?
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 UKís free range hens (approximately 9 million) and other outdoor birds are
vaccinated to help in the fight to keep avian flu out of the UKís poultry
15. Wouldnít it be cheaper just to move the free range hens
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.
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 suitable
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
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
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