The Food and Drug Administration approved the new swine flu vaccine Tuesday, a long-anticipated step as the government works to get vaccinations under way next month.
Health and Human Services Secretary Kathleen Sebelius announced the vaccine's approval to Congress - and said she hopes to get the first limited supplies distributed early in October.
The bulk of vaccine will start arriving Oct. 15, and Sebelius said it should be available at 90,000 sites around the country.
"We will have enough vaccine available for everyone" eventually, Sebelius said - everyone who wants it, that is.
The government has ordered 195 million doses for now but may order more if needed, she said. Typically 100 million Americans seek flu vaccine every year.
"There's no doubt we're in a race - .the virus versus the vaccine," Dr. William Schaffner of the Vanderbilt University Medical Center told CBS News medical correspondent Dr. Jon LaPook. "So the sooner we can get the vaccine and get it into people, the more likely we are to truncate this epidemic."
Swine flu information on the Web
But the vaccine, which protects against what doctors prefer to call the 2009 H1N1 flu strain, won't arrive all at once. About 45 million doses are expected by mid-October. That's why the government wants the people most likely to catch swine flu, and to suffer complications from it, to be first in line - including children and pregnant women.
FDA licensure means that the government has certified the vaccine is made properly and meets specific manufacturing and quality standards. Separately, the National Institutes of Health is studying the vaccine dosage and safety.
The FDA said that in clinical studies, a single does has proven effective for adults, who achieve full protection eight to 10 days after the dose is administered. The agency said that dosing for children is still being studied and that all dosing information is subject to change as clinical studies continue
The vaccine approval is timely. The CDC has found that flu activity is increasing around the country and has been found in all 50 states. For the week ending Sept. 4, nearly 5,000 new cases surfaced on college campuses, LaPook reports. The Southeast (2,414 cases) and Mid-Atlantic (515 cases) were hardest hit.
And new studies indicate the H1N1 virus lingers longer than previously thought. One study found 40 percent of patients may still be contagious seven days after symptoms began.
"I think we're learning that this virus is the seasonal virus, a little bit on steroids." Schaffner said. "It seems to be spread for a more prolonged period of time after people get completely well."
That's another reason why the government is promoting prevention, through a lighthearted public service announcement contest on YouTube, featuring entries such as this one.
The vaccine approved Tuesday is made by CSL Ltd. of Australia; Switzerland's Novartis; Sanofi-Pasteur of France; and Maryland-based Medimmune, which makes the only nasal-spray flu vaccine.