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So what is the score with Avian flu vaccines?
James Irvine
Teviot Scientific, Edinburgh & Perthshire
Filed 26th Feb 06
©www.land-care.org.uk
Vaccination in relation to the highly pathogenic
strain of avian influenza virus H5N1 can be considered under two
headings:
1. Vaccination of poultry and other animal species
2. Vaccination of people in the event of the virus
infecting man; and particularly should the virus mutate so that
man-to-man infection occurs, threatening a pandemic.
With the global spread,
and now the arrival in the EU of the
lethal H5N1 strain of avain flu, should domestic poultry be kept
housed
and should they be vaccinated?
Vaccination of poultry and other animal species
As recently reported (1)
France and Holland have been given permission by the European Commission
to carry out preventative vaccination, if they so wish. France has
now started. More than 350,000 geese and ducks raised for foie gras
are among birds to be vaccinated this week as France attempts to
to stall the spread of the virus.
Following the slaughtering of infected domestic
poultry in Germany in the vicinity of the Island of Reugen, France
suffered its first slaughtering of a commercial turkey farm following
infection with the highly virulent H5N1 strain of the avian flu
virus. More than 11,000 birds were involved.
France is Europe's biggest poultry farmer, and
France cares deeply for its farming. The French government recently
ordered avian flu vaccine for use on poultry from vaccine maker,
Intervet.
Intervet
The vaccine ordered by the French is against a
different strain of the virus, namely H5N2. While such a vaccine
may facilitate distinguishing vaccinated from infected birds, it
is unlikely to be maximally effective against the primary culprit,
H5N1.
However, a paper by Ellis et al, published in
the journal Avian Pathology in 2004 reports that the use of this
vaccine was effective in relation to the Hong Kong outbreak of Avian
flu H5N1 in 2002/3 (2). Contrary
to what is currently stated about such vaccines by DEFRA (see below),
the use of this vaccine did not result in evidence of post inoculation
asymptomatic shedding of the virus. The paper claims to provide
evidence that H5 vaccine can interrupt virus transmission in a field
setting.
Moreover, in spite all the warnings of just how
dangerous this particular virus is and evidence of its global spread
since 2003, it was only now that France asked the European Commission
(EC) for permission to use preventative vaccination, and it is only
in the past few days that the French government placed on order
with Intervet for H5N2 avian flu vaccine. Since it does take some
3 weeks after inoculation for the vaccine to achieve its maximum
effect (albeit perhaps limited by its nature), it would appear that
the French have got themselves into a very difficult position. If
they had used the vaccine three weeks ago they would have gained
what benefits it could provide, but the fear now must be that they
are trying to put the lid on the bottle after the genie has got
out.
Vaccination against avian influenza has been widely
practiced outside the EU.
The decisions on such matters as vaccinating livestock
within the 25 EU member states is taken by the EU's standing committee
on the food chain and animal health, made up of national veterinary
experts from all 25 member states. On the first day of the meeting
last week Germany, Austria, Denmark and Portugal raised strong objections,
while Britain voiced concerns about what vaccination could achieve
but had "no philosophical disagreement".
The only countries to apply for permission to
use preventative vaccination against avian flu H5N1 were France
and Holland. The anxiety level in France must currently be extremely
high, perhaps not helped that their neighbour Germany - who has
also suffered infection of domestic poultry - is not so far adopting
vaccination in the effort to prevent further spread. Yesterday a
wild duck found dead near Lake Constance in south west Germany tested
positive for the H5N1 strain. That is at the opposite end of Germany
from where the first positive test was found.
The UK stance about vaccination of poultry against
H5N1 is well described by Philip Clarke, European editor of Farmers
Weekly writing on 23 Feb 2006 (3).
Clearly DEFRA has set its face against preventative vaccination
of the UK's commercial poultry stock. But the reasons for choosing
this line of inaction are less than convincing, and are strongly
reminiscent of the dithering and misinformation that went on by
the comparable authorities in relation to FMD UK2001 (4).
Clearly the EC cannot be relied upon to come up
with a coordinated policy at an appropriate time, given the years
of warning it has had over the threat of global spread of this highly
virulent virus. Not only that, but it appears to get itself tied
in knots over its own designations of what is defined as "FMD-free"
or "avian flu-free", thus compromising trade unnecessarily.
One would have thought that DEFRA (along with the EU authorities)
could have announced a derogation in relation to the designation
of "organic free-range" for poultry and eggs in the event
of poultry having to be housed as a preventative measure against
the spread of avian flu long before 23rd February 2006.
In the UK it is extraordinary that DEFRA with
its veterinary officials have decided to take no action other than
"to be vigilant" even when the threat has come so close.
The incredulous statements that the UK is "well prepared",
"is equipped with many experts" and 'we managed fine with
our stamp out policy in a previous outbreak in 1992" undermines
confidence. Today the situation is very, very different from 1992.
Vaccination of people in the event of the virus infecting man;
and particularly should the virus mutate so that man-to-man infection
occurs, threatening a pandemic.
While Britain is sitting on its hands regarding
the question of vaccinating its poultry - and would appear to have
no stocks of vaccine for the purpose - it has some plans least there
should be a pandemic resulting from the virus mutating so as to
facilitate bird-to-man and then man-to-man spread.
They plan to vaccinate key workers against the
common varieties of flu, on the basis that mutation of the avian
flu virus is likely to be facilitated in the presence of other viruses.
This would appear to be a logical step, but the risk to key workers
might have been reduced in the first place by vaccinating the poultry
to at least reduce the viral load.
Chiron Corp, USA and Baxter International
What the UK government has also just done is to
place a contract with Chiron Corp of the USA and Baxter International
for 3.5 million doses of avian flu vaccine directed against the
H5N1 strain for use in humans. The purpose of this order is allegedly
to protect key workers in the event of the virus mutating and causing
a pandemic through man-to-man spread. However, the vaccine manufacturing
industry has serious difficulties in trying to cope with such a
global threat, let alone meeting its present requirements (5).
The Chiron Corp claims that the vaccine will be
manufactured using its adjuvant MF59 to increase the strength of
the vaccine. At the time of writing it is not clear what method
of vaccine production will be used by the company. `it is understood
that using cell culture in this situation has difficulties on account
of the virus killing the cells.
There also appears to be some uncertainty as to
where the vaccine will be manufactured - at its plant in Italy or
its plant at Liverpool in the UK - and when.
The placing of the UK contract highlights the
problems faced by vaccine producers. Chiron is quoted as stating
that it should be able to manufacture the UK order during the break
between its seasonal flu vaccine manufacturing runs. Chiron already
has a contract with the US government dated October 2005 to supply
the same vaccine worth $62.5million. In the event it will only be
able to provide 70% of this order before it switches its UK flu
vaccine manufacturing operations back to making its seasonal flu
product, FluVirin. The switch will occur in March.
Initially it appeared that Chrion stated that
the UK order would be manufactured in Italy, but more recently it
has stated that its plant in Liverpool, UK will be used. The Liverpool
plant was shut down by UK regulators in October 2004 on account
of concerns relating to contamination. The closure led to Chiron's
inability to ship about 48 million flu jabs to the US in time for
the 2004/5 flu season, resulting in a national shortage. The Company's
plant at Liverpool has now been cleared for vaccine production by
both the UK and the US authorities.
Chrion has submitted samples of its current avian
flu vaccine containing adjuvant MF59 to European drug regulators
for approval.
It is widely speculated that Chiron Corp is due
to be acquired by Novartis later this year in a deal worth $5.1billion,
Novartis already owns 40% of the stock of Chrion.
The UK government has placed an order with Baxter
International Inc, Illinois, USA for 2million doses of avian flu
vaccine. The company states that it expects to deliver by the end
of this year. It is understood that it tends to use its technology
to produce a cell-based pandemic avian flu vaccine in conjunction
with the National Institutes of Health. The cell-based method would
result in quicker production than the current method which uses
chicken eggs. That project is due to start clinical trials later
this year.
There is clearly a great deal of uncertainty:
both about the methods of production and the capacity to manufacture
at a sufficient rate to meet existing contracts, even if all technical
problems are overcome.
The total worth of the contract signed by the
British government covering both the Chiron and Baxter contract
is $57.55million. The UK government in placing these contracts states
that it is investing in research as well as hopefully getting a
useful product. However this investment is in American companies,
not British or even European based.
For my money, I would back the technique recently
described by Gao et al, University of Pittsburgh in the Journal
of Virology (6), albeit that the
project is in its early stages. It sounds the most promising.
From the title of their paper the research clearly
involved animal experimentation and understandably so. In the UK
so much essential biological research has been disrupted by animal
rights activists, using both symbolic and physical violence, that
it can come as little surprise that the leaders in the area of vaccination
- probably the most important aspect of present day public health
- are to be found elsewhere.
©www.land-care.org.uk
References
1. Editorial (006). Update on
Avian flu: 24th February 2006.
See ANIMAL HEALTH - GENERAL Homepage, filed 24 Feb 06,
www.land-care.org.uk Click
Here to View
2. Ellis, T. et al (2004). Vaccination
of chickens against H5N1 avian influenza in the face of an outbreak
interrupts virus transmission.
Avian Pathology, vol 33, pp 405 - 412. (Click
Here to View pdf)
3. Clarke, Philip (2006). Avian
flu vaccination deemed unnecessary.
Farmers Weekly, 23 Feb 2006. (Click
Here to View pdf)
4. Irvine, James (2006). Avian
flu five years on from FMD UK2001: have we learnt anything?
See ANIMAL HEALTH - GENERAL Homepage, filed 23 Feb 06,
www.land-care.org.uk Click
Here to View
5. Hamilton, David P. (2005).
Avian flu may tax vaccine makers.
The Wall Street Journal 26th February 2006 (Click
Here to View pdf)
6. Gao, W. et al (2006). Protection
of mice and poultry from lethal H5N1 Avian Influenza virus through
adenovirus-based immunization.
`j. Virol. 80: 1959-1964 (for
abstract Click Here to View)
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