Bird flu vaccine could spread disease

Scientists in Britain say vaccinating poultry against the H5N1 strain of avian influenza could spread the disease faster if it is done badly.

Researchers from the universities of Edinburgh and Warwick found that when flocks are incompletely protected a phenomenon known as "silent spread" occurs. Fewer birds die so the virus is not detected as it spreads from farm to farm.

The researchers' report in Nature recommends that farms use unvaccinated sentinel birds to detect the disease. Otherwise, they say flocks must be at least 95 percent protected against the virus to guarantee against silent spread.

"Vaccination reduces the chance of birds becoming infected and reduces the amount of virus they shed and the time over which they shed it," said Nick Savill of the University of Edinburgh. "If vaccination is to be used it needs to be done extremely well or it could make the problem worse, rather than better."

The study was done for the Department of Environment, Food and Rural Affairs.

Copyright 2006 by United Press International