Since emerging last spring in Mexico, the virus, known as H1N1, has spread to at least 168 countries, causing more than 162,000 deaths, including 436 in the United States.
"Everyone recognizes that H1N1 is going to be a challenge for all of us", said John Brennan of the Department of Homeland Security. This is the first flu pandemic in 41 years.
Hundreds of Americans in eight cities are lining up for experimental swine flu shots in a race to get a vaccine out in case the new flu virus regains strength this fall and winter.
Sharon Frey, who is leading the government-funded testing at Saint Louis University, said scientists have been working late nights and weekends to organize the studies and recruit volunteers.
"Typically it takes a year to do this," said Frey, an infectious diseases expert. "I can tell you we're working at breakneck speed."
About 2,800 people will participate in the government-led studies. Saint Louis University will test 200 adults and 200 children. Also under way are separate studies by five flu vaccine manufacturers under contract with the government.
Health officials expect to have about 160 million doses available this fall, with the first batch sometime in September. The studies will test the safety and effectiveness of vaccines developed by drug makers and help determine dosage and whether it can be given with a seasonal flu shot.