Recent appearance of H5N1 HPAI across six European Union (EU) countries since the beginning of 2007 has re-focussed attention on vaccination as tool in the management of avian influenza. The EU’s food safety assessment body (European Food Safety Agency [EFSA]) has just given strong signals for future use of poultry vaccination together with approved drugs and procedures.
Mass vaccination has been recognised as an important way of calming consumer concern over health and integrity of the EU’s massive poultry flock with particularly large numbers of birds concentrated on the western side of the continent in United Kingdom, France, Netherlands, Germany and Italy.
Officials recognise that something must be done to prevent a repeat market performance of 2006 when consumption of poultry and poultry products crashed, by up to 70 per cent in some countries like Italy.
That said there is no unanimity amongst scientists and officials over benefits and risks of mass vaccination. Some fear that mass vaccination of domestic poultry may actually prevent efficient detection of this deadly H5N1 strain. The apparent ‘nod through’ given by EFSA could assist in resolving current differences amongst different member states about whether to allow poultry producers to vaccinate their flocks.
The EU has approved a number of vaccines and there were precedents from 2006 when both France and Netherlands were given permission for limited vaccination of specific types of poultry in particularly high risk areas.
EU authorised vaccines are considered safe with no harmful effects on poultry products and the dedicated vaccines recommended for chickens and ducks meet required quality standards. However EFSA indicated that more research is required for vaccination in other types of poultry before any approvals can be made. EFSA has said that vaccination must be accompanied by monitoring with accompanying use of unvaccinated ‘sentinel’ birds, so that any post vaccination disease transmission can be identified and assessed to prevent circulation of a field strain under the cover of mass vaccination.
They clearly have in mind what happened in some Asian countries where vaccination was been deployed but not always in the appropriate and proper way. In 2006 the European Centre for Disease Prevention and Control (CPCD) issued a strong warning that widely but improperly used vaccination programmes in countries such as China and Indonesia were actually impeding H5N1 detection when the zoonosis moved into its human dimension. Some experts claim mass vaccination can hide any H5N1 infection that survives in vaccinated birds and in doing so presents significant hidden dangers by allowing disease to spread under the ‘blanket’ of vaccination. Thus far the EC and EU member countries have resisted calls for mass vaccination of domestic poultry. Most requests have come from producers of free range and organic birds which are clearly most at risk from spread of infection by wild birds, and especially wild water fowl. Limited vaccinations were authorised last year following poultry outbreaks in France and Germany and in wild birds across at least a dozen countries.
There has been no human case H5N1 HPAI anywhere in the EU but with over 300 cases worldwide (most fatal) scientists remain concerned about prospects of a pandemic, especially if the disease is allowed to spread unchecked. Vaccination when conducted as it should be will surely reduce the chances of this happening, but if administered improperly and inappropriately could actually make things worse.
At least three countries (China, Indonesia and Viet Nam) have undertaken large-scale poultry vaccination programmes against H5N1 with the mass culling of millions of birds. Vietnam is the only country where experts are sure this has been conducted in an appropriate way, and as efficiently and comprehensively as possible. But even Vietnam currently facing a resurgence of poultry outbreaks and re-appearance of human cases after an 18 month gap has realised vaccination is no ‘silver bullet’ for H5N1. CPCD says "If poultry immunisation is efficient and well monitored it could reduce the population burden of H5N1 in poultry and hence the risk for humans". "Equally if it leads to the silent circulation of H5N1 in poultry it could actually increase the threat to humans in those countries and increase risk of co-infection with other influenzas. Falling numbers of reported human cases in countries practising large scale poultry vaccination may, therefore, be misleading,” they say. Ongoing fight against avian influenza in Europe has focused on preventing the virus spreading from wild birds to domestic poultry.Outbreaks in domestic poultry have now occurred in a number of countries including France, Germany, United Kingdom, Hungary and The Czech Republic, with outbreaks in wild birds in considerably more. In March 2006 the E C authorised limited vaccination of flocks in certain areas of the Netherlands and France with unvaccinated so-called ‘sentinel’ birds used as part of the disease monitoring programme. Vaccination ceased on 1 April 2006.
EC and EU member states additionally approved field research into vaccination programmes to be carried out in Germany. Germany is currently pursuing the research programme on three commercial farms in North Rhine Westphalia over a two-year trial period.Vaccination is carried out for research purposes only, as part of comprehensive field study to establish the effect against avian influenza. No birds from the study nor their meat and eggs will reach the market.