Washington ? The United States is ready to announce another $1 billion in orders for swine flu vaccinations.

Health and Human Services Secretary Kathleen Sebelius says she will announce today that Washington has approved another billion dollars to buy components of the vaccine. Sebelius said on Sunday that research is under way to provide a safe and effective vaccine to fight a flu strain that could be a pandemic.

Sebelius and other top officials are bracing for fall’s flu season. She says leaders are watching the Southern Hemisphere for clues how serious the U.S. flu season might be.

Sebelius appeared on CNN’s “State of the Union.”