This action is in response to rising fears about the spread of highly virulent avian influenza, which has resulted in the deaths of millions of birds, most of which were found in commercial poultry flocks.

In recent weeks, the World Health Organization (WHO) has issued a warning after cases of the virus strain jumping from birds to mammals were reported, urging the countries should prepare for the possibility of another pandemic caused by H5N1.

"Over the past few weeks, there have been several reports of mammals, including minks, otters, foxes, and sea lions, having been infected with H5N1 avian influenza," said WHO's Director-General Tedros Adhanom Ghebreyesus in a media briefing on global health.

"H5N1 has spread widely in wild birds and poultry for 25 years, but the recent spillover to mammals needs to be monitored closely. For the moment, WHO assesses the risk to humans as low," he added.

Now, federal scientists are preparing to test the first avian flu shots in years.

However,  vaccinating commercial birds isn't a straightforward solution since some people worry it will make it more difficult for the United States to export poultry products.

"The decision to proceed with vaccination is complex, and many factors must be considered before implementing a vaccination strategy,"  USDA spokesperson Mike Stepien told CBS News, adding that the inspection service is discussing its options and "soliciting input from many different industry stakeholders that would be impacted."

Stepien noted that while licensing animal vaccinations can take years, certain steps can be expedited in cases of emergency.