as far as i know all vaccination sheets must be filled out and signed by 2 other members of the union who act as wittiness basically saying that the birds have been done in accordance with legislation it is a terrible disease ive seen lofts been wiped out pigeons rolling around on there head and god only knows what effects it has on a pigeons inside while the vaccination is not 100% why take the chance on helping to inflict this disease on your birds as this virus has many ways of spreading not just from contact with other birds its airborne too i believe also may be passed on from entering another loft and bringing it back even on your clothes or shoes i also believe that birds that have been vaccinated get over this more quickly than others as there immune system has come up against a milder form of the virus though vaccination that why many top vets believe who are not involved with the makers of the vaccine so there no profit to be made from it from them say to even vaccinate twice once on weaning and again a month or so before racing i have to say i agree with this method i also think everybody should do there stock not just the racers