Global standard for avian vaccines needed – expert
By Patricia Reaney
The Star, 9 Dec 2005

LONDON (Reuters) - International standards should be set for avian vaccines to combat the spread of the deadly H5N1 bird flu in chickens, a leading virologist said on Thursday. 

Unlike influenza vaccines for humans which must contain a minimum amount of antigen to stimulate an immune response, no figure had been stipulated for avian vaccines, said Dr Robert Webster of St Jude's Children's Hospital in Memphis, Tennessee. 

"We should at least establish a minimal level," he told a briefing during a meeting on emerging diseases in London. 

"There are no international standards. There should be." 

Vaccinating chickens is a major weapon against the spread of bird flu.

Research has shown that vaccines can reduce the infectiousness of chickens with avian flu and the susceptibility of healthy birds to the virus. 

Birds immunised with poor quality vaccines look healthy but spread the virus at high concentrations in their faeces for a longer period of time, said Webster, director of the World Health Organisation Centre for Studies on the Ecology of Influenza in Animals and Birds at the Memphis hospital. 

"That is one of the difficulties," he told the meeting organised by Britain's Medical Research Council (MRC). 

Halting the spread of H5N1 virus, which is endemic in poultry in parts of Asia and has been found in birds in eastern Europe, is considered vital to prevent a human pandemic in which millions could die. 

H5N1 has infected more than 130 people in Asia and killed 69. Health experts fear the virus could mutate on its own or mix with a human influenza virus to create a strain that is transmitted easily from person to person. 

China, which has culled 20 million birds, has announced plans to vaccinate billions. There have been more than 30 outbreaks of bird flu in flocks across China this year. 

Webster and John Skehel, the director of the MRC National Institute for Medical Research, said China has the latest technology to produce the best poultry vaccines. 

Indonesia and Vietnam, both hard hit by bird flu, have also been urged to step up vaccination. 

Webster said scientists know the minimum amount of antigen needed to immunise a chicken. Although setting international standards for poultry vaccines would cost a bit more money, he said the advantages would be enormous. 

Webster also described migratory ducks as the "Trojan Horse" of bird flu because although they do not get the disease, they could be carriers of the virus.