JAKARTA, June 12 (Xinhua) -- Experts on Tuesday called on relevant organizations to conduct more researches to find out how significant avian influenza viruses have changed in Indonesia, in a bid to produce the right vaccine to check the development of the deadly viruses.

    Experts from the United States and Indonesia made the call during a seminar on avian influenza vaccination in Jakarta.

    An Indonesian expert from the Research Center for Biotechnology of Gadjah Mada University, Widya Asmara, said that there had been indication that the viruses had geographically changed.

    "It is urgent to conduct more researches to prove the change," he told Xinhua.

    If the change is significant, it will be necessary to develop anew strain of vaccine, he added.

    "There are some indications that some strains of the viruses have changed in some regions," he said.

    Another Indonesian expert, Ngurah Mahabarata, said that the highly pathogenic H5N1 virus so far had spread before it could control properly.

    "When the virus has a chance to infect poultry, it has a chance to develop and at the same time it changes its structure," he said.

    John Weaver, from the avian influenza control program of the United Nations in Indonesia warned of the risk when the virus changes.

    "We have to be aware that there is always a risk that the field virus is becoming more different," he said.

    Indonesia now has 12 registered vaccines for avian influenza, which produce a very high level of antibody, according to Weaver.

    Indonesia is the worst hit by avian influenza with 79 fatalities. The health authorities have vaccinate tens of millions of chickens in the vast archipelago country, but the virus still exists.

    Back-yard farm and the huge territorial size have made it difficult for Indonesia to halt the spread of the avian influenza viruses.

    Over 32 million families engage in back-yard farm in the country.