Effective vaccines for avian influenza in poultry not yet available

Vaccines have been developed to combat avian influenza in poultry and bird flu in humans. But scientists are reluctant to approve the mass vaccination of chickens because they believe it may not reduce the risk of infection. The vaccines appear to mask the symptoms so poultry keepers may not be aware that their birds are infected. This could allow the virus to spread widely and may cross over to humans. The vaccines developed for humans seem to be more effective in controlling the effects of bird flu.