The Chinese government has given the go-ahead to a Shanghai-based pharmaceutical firm to begin clinical trials of Tamiflu, an anti-viral drug that is believed to be the best defense against bird flu in humans.

The drug will be manufactured by Shanghai Sunve Pharmaceutical Co Ltd under a licensing arrangement with Swiss drug producer Roche.

The study will try to find out if the Tamiflu produced by the Shanghai firm is as effective as that produced by Roche.

Tamiflu is made from shikimic acid, which is found in star anise, often used as a spice in Chinese cooking.

In Beijing, Jia Youling, national chief veterinary officer, said on Saturday that if the immunization policy is carried out properly, possibilities of a bird flu outbreak in many areas will be sharply reduced.

At a press conference held by the Ministry of Agriculture, Jia said the country has provided 2.967 billion vaccines to local departments to stem the spread of bird flu.

Most of the areas will be well prepared by the time migratory birds fly north in mid-April, Jia said.

At the same time, relevant departments are ready to make new vaccines to cope with any variants of the virus, he said, adding the vaccine that has been developed can prevent the current virus.

"The most crucial measure is that all fowls must be injected with the vaccine," he said.

Since China took such measures from October 2005, the spread of bird flu has been contained, Jia said. Three outbreaks have been confirmed so far this year, 46 less than during the same period in 2004. The 35 cases reported in 2005 have all been controlled.

As the virus can easily spread during spring, the ministry has urged local departments to be high alert, Jia said.

The ministry has sent 28 supervisory groups to different regions of the country to inspect their work, and the preparation is satisfactory, he said.