The following outlines the Soil Association's position on the use of vaccination for poultry in the control of avian influenza.

Summary and key points
The Soil Association sees vaccination as a key strategy to protect public health and reduce the likelihood of wholesale confinement and culling of poultry. On the basis of its research and a review of evidence from around the world, the Soil Association believes that vaccination should be one of the tools the UK Government adopts for the control of avian influenza.

Should an outbreak of avian influenza occur, the best use of vaccination would be as a ring fence – in other words, surrounding and seeking to contain the spread of the disease. This allows for monitoring of flocks outside the vaccinated ring fence.

The European Union position is that vaccination can be used and is the method of control endorsed by both the UN Food & Agriculture Organisation (FAO) and the World Organisation for Animal Health (OIE). Yet despite this, the UK Government (Defra) does not currently 'expect' vaccination to be part of its avian influenza control strategy.

The Soil Association is lobbying Defra to change its position on the use of vaccination as a key control tool. Urgent action is needed, given the potential for an imminent outbreak and the fact that it will take at least three months to produce sufficient stocks of vaccine, as well as the need to train those who will administer the vaccine to poultry flocks.

Key points:

• Vaccines for avian influenza do exist and it is possible to differentiate between an infected and a vaccinated bird
• Vaccination has been used effectively in other countries as control measures for both low pathogenic and high pathogenic avian influenza – including for the H5N1 strain potentially threatening UK poultry
• Yet the UK Government (Defra) is currently only advocating the use of vaccine for zoological collections and rare or endangered birds
• Other EU countries, such as Spain, have stockpiled sufficient supplies of vaccine to undertake an effective ring-vaccination control strategy. Currently, the UK has none
• Building up sufficient stocks would require at least three months to produce the vaccine, plus three months potency testing
• There is no disagreement on control strategies for controlling viral diseases in humans: vaccination is the first and most efficacious approach. Confinement and mass-slaughter are not recommended strategies…
• Following the devastating outbreak of foot and mouth disease (FMD) in 2001, the EU policy is to use vaccination and not rely on a culling policy. An EU repository of FMD vaccine has been set-up.

Vaccination – a critical tool in early stages of any outbreak
It is claimed that vaccination only reduces shedding of virus, rather than completely eliminating it. However, it is likely to significantly slow the progress of the disease. In an outbreak of avian influenza, reduction of virus circulation is a critical factor in preventing spread of avian influenza to other birds and to people. Reduction of virus excretion significantly reduces the chance that an infected farm will infect another farm.

Precedents for vaccinating individual birds
There are logistic and potential welfare issues to consider with vaccination, as each bird has to be injected individually. This would have to be undertaken by trained teams to ensure vaccine is delivered correctly whilst minimising stress. However, there are precedents for this – for example, during outbreaks of poultry diseases, such as Gumboro, birds already on the ground have been vaccinated. As well as urgently building up stocks of the appropriate vaccine, a programme to train sufficient personnel to administer the vaccination effectively and humanely is a priority.

Costs of vaccines are not excessive
The cost of vaccination is likely to be similar to that of other inactivated vaccines – in other words, up to £0.10 per bird plus up to £0.03 cost of giving the vaccine.

Ring-vaccination appropriate – not mass vaccination currently
Mass vaccination is not an appropriate response to the current level of risk. It would also be difficult to carry-out as the whereabouts of many birds – especially small-scale hobby poultry keepers – is unknown.

Adopting mass vaccination at this stage would still mean birds would be likely to need booster injections if the disease arrived. It could also make monitoring of the progress of the disease more difficult, although it is possible to differentiate between vaccinated and infected birds. It is also arguable that mass vaccination could encourage farmers to relax biosecurity measures.

The Soil Association accepts that in an emergency situation, such as the potential outbreak of avian influenza, targeted vaccination is an appropriate response. However, any move to mass vaccination compromises the long-term objectives of organic, sustainable husbandry to raise livestock with robust, natural immune systems that are more able to resist disease challenges.

Successful use of vaccination in other countries
In the face of a substantial epidemic, countries that adopted vaccination have had better overall results in controlling their outbreaks than countries that did not (see reference 2).

Hong Kong:
Hong Kong has gone through the entire 2003/2005 epidemic without a case in commercial poultry or people. This is despite the extensive infection in nearby countries, importation of live poultry over most of this period from China, and fairly regular detection of infection of wild birds.

Hong Kong demonstrates that successful control is possible using an integrated control approach, progressively adjusting measures to achieve effective control. An H5N2 vaccine was used against H5N1 infection.

During the early incidences in Hong Kong stamping out of the disease by culling was used very effectively. As the incidents continued to arise, separation of species in the markets, the use of rest days to reduce virus exchange within the markets and the banning of some birds (such as quail, ducks and geese) from live marketing, substantially improved control but did not completely stop new outbreaks. Ultimately, vaccination and strict biosecurity were introduced.

Once infection has become endemic in medium-sized reservoir species, such as domestic ducks, stamping out alone is unlikely to succeed and a more integrated approach must be adopted – that is one that includes vaccination.

Italy:
Following confirmation of low pathogenic avian influenza, vaccination against the disease is currently being applied in some regions of Italy, pursuant to the European Commission Decision 2005/10/EC.

The vaccination strategy developed and applied in Italy makes use of a heterologous (of different origin, such as an H5N2 vaccination for an H5N1 outbreak) vaccine allowing discrimination between vaccinated and infected poultry.

Mexico and the United States:
Research and field experience in Mexico and the United States has shown that vaccination for avian influenza can decrease the clinical signs of avian influenza, decrease the viral shed from known infected birds and therefore decrease the potential transmission of the disease to surrounding flocks (see reference 1).

Indonesia and China:
Vaccination was applied to control infection in Indonesia and China and to prevent infection in Hong Kong. In 2003, Indonesia made extensive use of vaccination in addition to heightened biosecurity and movement restrictions. This method appears to have bought its previously widespread epidemic under control. Whilst the evidence from Indonesia and China is circumstantial and not based on scientific trials, vaccination appears to have been very beneficial in reducing the virus load to which populations were exposed, shortening outbreaks and preventing long term maintenance of an infected state.

UK Government (Defra) currently stated position on vaccination:
There is provision in the Diseases of Poultry (England) Order 2003 for the imposition of a compulsory vaccination zone.

"However, in view of the limitations, summarised below, vaccination is not expected to be part of the current UK avian influenza control strategy. However, there may be a role for vaccination in the protection of zoological collections of rare breeds or endangered species. Such use would be subject to a Commission Decision adopted by the Standing Committee on Food Chain and Animal Health in Brussels." (quoted from Defra website).

• Defra's position: The vaccines that are currently available to protect against avian influenza are inactivated types and need to be delivered by injecting birds individually. It can take up to three weeks for birds to develop optimum protective immunity and some poultry require two doses. Delivering such a vaccine, as an emergency measure, to large numbers of birds can raise significant logistical difficulties.
• Soil Association response: There are logistic problems to delivery of a vaccine, but they are not insurmountable. There is precedent with other diseases for going onto farm and vaccinating birds. It will take time for birds to develop full immunity, but vaccination will still slow the spread of disease.

• Defra's position: These vaccines protect against disease but will not protect birds from becoming infected and shedding virus. Although vaccination will reduce the amount of virus shed by birds and hence the viral load, this reduced amount may still be significant and could cause infection in other birds.
• Soil Association response: Even if the vaccinated birds are still shedding virus the amount of virus shed is markedly reduced. This will certainly slow the spread of the disease. If birds are vaccinated the chances of the disease spreading to other farms is much lower.

• Defra's position: Although there are strategies to differentiate vaccinated birds from infected birds, such as the use of DIVA (Differentiating Infected and Vaccinated Animals) and keeping unvaccinated 'sentinel' birds, vaccination may lead to difficulties in identifying birds that are carrying the virus; this can be a problem for control.
• Soil Association response: There is good evidence that differentiation techniques are effective. Additionally, if we are just using vaccine as a ring fence we would have three zones:
  i. where an outbreak has occurred and culling has taken place
  ii. the vaccinated zone
  iii. a surveillance zone where vaccination has not been actioned, but a high-state of vigilance for any signs of new outbreaks is maintained.

• Defra's position: No avian influenza vaccines currently have marketing authorisation in Great Britain.
• Soil Association response: Marketing authorisation is a paper exercise that should not present a major obstacle or be used as an excuse for inaction.

European Union position
In accordance with Directive 92/40/EEC vaccination against avian influenza may be used to supplement the control measures carried out after confirmation of disease. Birds vaccinated against the HA subtype corresponding to the one which is circulating are protected against the worst effects of avian influenza.

The decision to introduce vaccination may be taken by the Member State concerned, with or without prior approval by the Commission. Such steps must be accompanied by further disease control measures including trade restrictions, in accordance with the Standing Committee procedures (For wording of 92/40/EEC see Appendices).

Vaccination – for and against (see reference 3)
Against:

• The use of vaccine does not encourage farmers to improve isolation, disease control or biosecurity measures
• Vaccination can successfully prevent signs of the disease, but does not completely prevent virus shedding
• The use of vaccine can affect trade and mask residual infection

For:

• Vaccines can prevent disease and save the poultry industry of a country from collapse, especially if the outbreak is widespread
• Vaccines reduce the virus load and the likelihood of transmission, including transmission to humans and the possible emergence of a pandemic strain
• There are techniques to distinguish between vaccinated and infected birds
• Vaccinated birds are eventually eliminated by slaughter and processing for food and virus eradication is declared only when all the poultry in the area are serologically negative
• There is no disagreement on control strategies for viral diseases in humans: vaccination is the first and most efficacious approach.

We know there are vaccines available and there are techniques for differentiating between vaccinated birds and infected birds, but there is concern that vaccination may not protect entirely against infection or transmission. It does seem clear that shedding of virus is markedly reduced in vaccinated birds.

There is a time lag between vaccination and development of immunity and the vaccine needs to be injected into each individual bird so there are some logistical issues with use. Getting qualified people in sufficient numbers to inject poultry in houses with no available herding or handling space makes this task very difficult and stress inducing (stress being the biggest immuno-suppressant in poultry).

So far we believe avian influenza vaccines have only been used on low pathogenic avian influenza, except in Hong Kong from where there is a scientific report on how vaccination was used to ring fence an outbreak and prevent spread of the disease. Therefore, the Soil Association's current view is that ring fence vaccination is the most effective and proportionate strategy to adopt, initially to protect human health whilst reducing negative impacts on the organic and free-range poultry sector.

References

1. Davison S., Scott P. and Eckroade R. J. (1998) Avian Influenza Vaccination, Bellwether – The Newsmagazine of the School of Veterinary Medicine, University of Pennsylvania, 43 http://www.vet.upenn.edu/schoolresources/communications/publications/bellwether/43/articles.html#avian
2. Morris R. S. and Jackson R (2005). Epidemiology of H5N1 Avian Influenza in Asia and Implications for regional control. A report for the Food and Agriculture Organisation of the United Nations covering the period January 2003 to February 2005. Massey University, NZ
3. Webster R. G. and Hulse D. J. (2004) Microbial adaptation and change: avian influenza. Rev. sci. tech. Off. Int. Epiz., 2004, 23(2) p453-465

Appendices

Appendix 1: Wording of EC Directive 92/40/EEC
Introducing Community measures for the control of avian influenza
Whereas it is necessary to prevent any spread of disease as soon as an outbreak occurs, by carefully monitoring movements of animals and the use of products liable to be contaminated, and where appropriate by vaccination.

Vaccination against avian influenza with vaccines authorised by the competent authority may only be used to supplement the control measures carried out when the disease appears and in accordance with the following provisions (provisions are concentration of poultry, characteristics of vaccine, and so on).

Once the diagnosis of avian influenza has been officially confirmed the Member States shall ensure the competent authority establishes around the infected holding a protection zone based on a minimum radius of three kilometres itself contained in a surveillance zone based on a minimum radius of 10 kilometres.

Appendix 2: Information from Morris and Jackson (2005) Report for the Food and Agriculture Organisation (see reference 2)
Vaccination is a very important method of managing risk during production and has been beneficial in some countries. Vaccination does not have to be universal, but may in the first instance focus on high risk groups, with the aim of reducing transmission from these, so that onward transmission from these, so that onward flow of infection is reduced. In current circumstances, reducing virus excretion is an urgent requirement, so the concern that vaccination may not protect entirely against infection or transmission is less important than reducing virus excretion overall.

One of the conclusions from this report was: The most valuable tools at present are vaccination, market management, risk based local control action, movement control at key locations and enhanced biosecurity through measures such as separation of reservoir and spillover species during production and marketing.

Although there is continuing debate about the pros and cons of vaccination the immediate priority is to protect the human and domestic poultry population from highly virulent strains by reducing the amount of virus circulating. The evidence supports vaccination as a tool for achieving this. Vaccination can be selective in order to block transmission in key populations and geographical locations and does not have to be applied universally.

Appendix 3: Information supplied by from companies producing vaccines
Efficacy
Intervet has carried out trials using avian influenza vaccines. Their experiment showed that both H5 and H7 vaccines induced complete protection against clinical disease and mortality. After disease challenge virus excretion was prevented in the majority of birds. In the birds that excreted virus the average virus levels were between 10,000 and 100,000 times less than in the non-vaccinated birds.

The report added that the vast majority of vaccinated birds exposed to field virus do not become infected. For the few vaccinated birds that might become infected, shedding of virus is markedly reduced (both in the duration of excretion and the quantity of virus).

The important thing is the 'H' part of the vaccine: this needs to match the outbreak. Therefore, an H5 vaccine will work on an H5 outbreak and an H7 vaccine on an H7 outbreak but not vice versa. There are bivalent vaccines available that cover both H5 and H7. The use of oil emulsion adjuvants gives the vaccines a broader coverage.

There is some data from the vaccine companies that shows that vaccination stops shedding of infection rather than just reducing it.

Differentiation
The 'N' part of the vaccine is what is used to differentiate between a vaccinated bird and an infected bird. So in an outbreak of H5N1 a vaccine such as H5N9 could be used. The method of testing is the DIVA test (Differentiation of Infected versus Vaccinated Animals). There is a rapid plate test as well that can be used.

Availability
It will take three to four months to provide new supplies of vaccine. This vaccine would be tested as being 'safe' but the potency testing would take another three to four months.

There is a live vaccine as well – this would take two months to produce plus the potency testing.

If you have to fire fight you could use the 'safe' vaccine, but without the potency testing you do not know whether its actually going to work. If Defra agreed to use vaccination as part of its response to control avian influenza then it must be ordered now to give the vaccine companies time to build up the supply.

Administration
The inactivated vaccine cannot be given in the first week of age – it is given at seven days and then takes 10 to 14 days to build immunity. The live vaccine can be given to day old birds and within a week they will develop immunity. Turkeys will need more than one dose to develop immunity.

It is not unheard of for both broilers and layers to be caught and vaccinated once they have been placed on farm. When Gumboro was first a problem and a vaccine was developed table birds were caught and vaccinated.

Restrictions on vaccinated products
Italy has been vaccinating for avian influenza for some time on a prophylactic basis. There are some restrictions on meat and poultry products from vaccinated flocks – live poultry and eggs cannot be exported and meat must have a stamp to show it has been produced from a vaccinated flock.

Time to develop immunity
Treatment to efficacy is around two weeks after one dose of vaccine. This will not prevent shedding but will prevent physical symptoms. Some birds such as turkeys and breeder flocks will require more than one dose of vaccine.

Other EU countries
The Dutch are asking for backyard poultry producers to vaccinate their birds – but not commercial flocks.

The Spanish are reported to have a fully potency tested vaccine bank ready for use. The French have just ordered vaccine and 40 million doses have been supplied to the United States Department of Agriculture (USDA).

Mass vaccination?
The vaccine companies suggest that vaccine could be used prophylactically now to vaccinate all birds. If there was an outbreak it is likely that birds would have to be re-vaccinated but this would put us in the position of boosting a basal level of immunity rather than developing immunity. This would be quicker. However, the veterinary advice we have is that ring fence vaccination in the event of an outbreak is the most appropriate action. This allows continued monitoring of the disease within the vaccinated area and a further designated zone around that.

Cost
The cost of vaccination is thought to be equivalent to the cost of other inactivated vaccines currently used. This is anywhere between £0.04 to £0.10 a bird, plus a cost of £0.02 to £0.03 cost of administering the vaccine.

For further information please call the Soil Association food and farming department on 0117 914 2400

Published: 26/10/2005

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