The new vaccines are safer and more effective than previous versions developed in China and abroad, the ministry's spokesman said.

Laboratory studies showed the two new vaccines can produce extremely strong antibodies that target the H5N1 virus and remain effective within an animal's immune system for as long as 10 months, much longer than other vaccines of its kind, scientists said.

Developed by more than 30 Chinese scientists from two key national laboratories, the new vaccines have received preliminary approval from the National Agricultural Bio-Safety Committee and the ministry's Animal Medicine Evaluation Committee.

Having demonstrated safety and efficacy in limited trials, the new vaccines have been put into large-scale production and are expected to be used widely on poultry and other birds.

"The new vaccines will give the fight against bird flu a powerful boost, both in China and the rest of the world," said a Ministry of Agriculture spokesman.

The virulent H5N1 strain of avian influenza virus is proving difficult to stamp out, with new and recurring outbreaks among poultry despite the slaughter of 100 million birds. Experts said culling is by far the most effective way to combat the disease, although it can also be devastating to farmers unless they get help.

Meanwhile, the WHO influenza network has decided to provide China with prototype vaccine strains to assist developing a bird flu vaccine for humans, said Roy Wadia, of the WHO's China office.

The prototype vaccine is likely to be available by the end of this month and will be given to pharmaceuticals makers around the world, including China, which can produce batches for first-phase clinical tests on humans, he added.

Meanwhile, on Thursday Hong Kong started accepting applications for the importation of chilled and frozen poultry meat from the mainland.

Hong Kong officials said they monitored the bird flu outbreak situation on the mainland very closely before deciding to resume the imports.

(China Daily March 12, 2004)