WASHINGTON, Nov. 28 (Xinhuanet) -- Vaccines can protect poultry from bird flu and block viral spread between birds, showed a Dutchstudy published in the Monday issue of Proceedings of the National Academy of Sciences.

    Researchers in the Netherlands tested two vaccines targeting the H7N7 bird-flu strain, and found the vaccines were effective in stopping the spread of the viral strain between chickens.

    The study was conducted after reports of asymptomatic chickens shedding virus after vaccination. Previous research found vaccination could protect individual chickens from falling ill with various flu strains.

    In the study, healthy vaccinated chickens were housed together with infected ones. Researchers found the virus' reproduction ratewas brought down enough to enable only a small number of new infections in the two weeks after inoculation. Some transmission occurred in the first following week, reported J. A. van der Grootand colleagues from the Netherlands' Central Institute for Animal Disease Control.

    The researchers said the vaccines worked at different levels of effectiveness, and this made it necessary for health authorities to test vaccines' ability before poultry inoculation.

    The H7N7 bird flu strain used in the study is different from the H5N1 strain that has led to at least 68 deaths among humans inAsia since 2003. It is feared that the H5N1 strain could mutate quickly to be easily transmissible among humans, causing a global epidemic.

    Some Asian countries have vaccinated chickens to control the bird flu outbreaks. The United Nations Food and Agriculture Organization has recommended targeted vaccination of poultry as one measure to contain the spread of bird flu. Enditem