August 17, 2006

UK study says vaccination can worsen spread of bird flu

Mass vaccination of poultry flocks against bird flu could make the spread of H5N1 worse, Scottish scientists have found.

An Edinburgh University study concluded that, even though the available vaccines are effective on individual birds, the disease is likely to spread unless more than 95 percent of a flock has been protected.

Vietnam and Indonesia, two of the countries worst hit by bird flu, have instituted mass vaccination programmes.

On the other hand, UK authorities have rejected vaccination, taking the stand that such a move would only disguise the spread of a larger outbreak.

The disease would spread through immunised birds which are still vulnerable to the disease and are capable of passing it on without presenting any symptoms themselves, UK authorities claimed.

Therefore, as protection levels rise in a vaccinated flock, it would become harder to detect the spread of avian flu, as fewer deaths occur.

However, the virus would still be lurking around in farms, requiring ever more vaccines to suppress it.

The study, led by Dr Nick Savill, of the university's centre for infectious diseases, found that it is very hard to protect more than about of 90 percent of the birds in any given flock and usually, the actual protection offered by these programmes would be much lower.