In Belgium, the vaccination of exotic birds in zoos has begun, as part of efforts to stop the spread of avian flu, despite questions over whether vaccines will be effective.At the moment there is only a vaccine against the H5N2 strain of the virus, which is not as strong as H5N1. Vets have been given four days to vaccinate all exotic birds in the country. “Without analysis you can’t find out if the animals are going to be protected or not,” said vet Francis Vercammen. “Blood samples are taken from the animals, so we canfind out how many antibodies the animals have developed.” And that is one of the problems: uncertainty about the vaccine’s level of protection. The EU has a programme to carry out tests, to evaluate the protection from disease and to find out whether vaccinated birds are still carriers of the virus. Vets are also raising questions about the vaccination of poultry. “The animals are not clinically sick,” said Professor Bernard Toma, from a veterinary school in France. “But that doesn’t totally rule out the fact that in the case of contamination the virus could multiply a bit in the organism.” Experts say vaccinated animals that appear to be healthy could in fact be storing the virus, making eradication more difficult. Any vaccination of poultry would be a massive exercise: in France alone, 700 million birds are bred every year. It remains to be seen whether there would be enough vaccine, given each bird would need two doses.