The US Department of Agriculture (USDA) said on Wednesday that a bird flu vaccination is not enough to be approved for emergency use against the current outbreak that has badly affected the Midwest poultry industry.

The USDA’s Animal and Plant Health Inspection Service said in a statement on Wednesday that the present vaccine available to combat bird flu does not match well against the highly pathogenic H5N2 virus.

Experts said the vaccine is also not capable to provide sufficient protection from the infectious virus. “The vaccine currently available offers just 60 % effectiveness in chickens, leaving 4 in 10 birds unprotected. The vaccine's effectiveness in turkeys is still being studied”, it said.

As per the USDA’s count, bird flu so far has cost chicken and turkey producers more than 45 million birds since early March, mostly in Iowa and Minnesota.

The USDA said it will continue to make efforts to develop some more and effective vaccines, and will also re-evaluate it decision for those vaccines that are already in use.

The agency said from now onwards, it will carefully consider both the efficacy of any new vaccine and the potential foreign trade losses.

But a major concern raised by the agency is that several significant US trade partners have told the USDA that they might ban all imports of US poultry and eggs, which could cost producers billions of dollars in lost exports.

If a vaccine is ultimately approved, the USDA said it would be targeted to the states and poultry sectors where it could be most effective.