# 2124
While the use of poultry vaccines is controversial, and certainly not universally accepted, in many countries where the H5N1 bird flu virus is endemic their use is widespread.
The concern has always been that vaccinated flocks could contribute to the silent spread of the disease due to incomplete protection from the virus, resulting in asymptomatic, but infectious birds.
In 2006, Vietnam's vaccination program was hailed as having brought containment and control to that bird flu ravaged nation. Despite its critics, it seemed that vaccination programs were effective.
Over the past year, however, we've seen more reports of asymptomatic, but infected, birds. In some cases, in previously vaccinated flocks.
Now we are getting this warning, from Professor Yuen Kwok-yung of Hong Kong, that the H5N2 poultry vaccine being used to protect birds is losing its effectiveness.
This story from Monsters & Critics. Follow the link to read the whole thing.
Hong Kong expert warns flu vaccine for chickens losing efficacy
Jul 8, 2008, 4:19 GMT
Hong Kong - A vaccine used to stop outbreaks of the deadly bird flu virus in chickens in Hong Kong for the last seven years is losing its effectiveness, a leading microbiologist warned Tuesday.
Professor Yuen Kwok-yung said the vaccine, which protects chicken from the H5 strain of the virus, is becoming less effective and the city risks further outbreaks because total failure is inevitable.
The head of microbiology at the University of Hong Kong told the South China Morning Post the virus was mutating and shifting away from the Fujian strain of H5N2 that it was developed for.
His warning follows an outbreak of H5N1 virus in four wet markets in Hong Kong in June, the first in years in the former British colony.
Yuen, who is part of a team investigating the outbreak, said the city must get rid of all live chickens in markets before the vaccine becomes completely ineffective.
He said tests showed that in 2005 vaccine was producing only a quarter of the antibodies to protect against the virus compared to the level produced by the same vaccine in 2001.
He said some chickens showed an antibodies level at the 'alarm stage' which meant the protection was minimal.
