y LAURAN NEERGAARD, AP Medical Writer Lauran Neergaard, Ap Medical Writer Tue Sep 15, 5:17 pm ET
WASHINGTON The Food and Drug Administration approved the new swine flu vaccine Tuesday, a long-anticipated step as the government works to start mass vaccinations next month. Limited supplies should start trickling out the first week of October about a week earlier than expected, Health and Human Services Secretary Kathleen Sebelius told Congress. Then about 45 million doses should arrive around Oct. 15, followed by more shipments each week.

She said they'll be available at up to 90,000 sites, including schools and clinics, across the U.S. that state health departments have chosen as best at getting the shots out fast.

Eventually, "we will have enough vaccine available for everyone," Sebelius said. Everyone who wants it, that is.

The government has ordered 195 million doses but may order more if there's enough demand, she said. Typically fewer than 100 million Americans seek flu vaccine every year, and it's unclear whether swine flu what scientists prefer to call the 2009 H1N1 strain will prompt much more demand. A recent Associated Press-GfK poll found 57 percent of people said they were likely to get it.

This year is unusual: Many people will have to line up twice for flu vaccine, once to be inoculated against regular winter flu and a second time for an H1N1 vaccination.

The new swine flu seems no more deadly than regular winter flu, which every year kills 36,000 Americans and hospitalizes 200,000. But there's an important difference: This H1N1 strain sickens younger people more frequently than the people over 65 who are the main victims of seasonal flu.

So the government wants certain people in line first for the H1N1 vaccinations: Pregnant women; the young, from age 6 months up through age 24; and people younger than 65 who have flu-risky conditions such as asthma, diabetes or heart disease; caregivers of the at-risk, including newborns; and health workers.

The vast majority of people who get swine flu "so far are not terribly ill," Sebelius noted, saying most will recover fine at home with some rest and fluids. And they shouldn't race to doctors' offices seeking tests to find out what kind of flu they have H1N1 or the regular strains that circulate every winter because treatment is the same.

"The flu is the flu is the flu right now," Sebelius said.

Nor should doctors hand out prescriptions for anti-flu medicines to be used to prevent flu, she added, because "it could make them sicker in the long run."

The drugs Tamiflu and Relenza should be used for treatment only, she stressed.

Sebelius announced the FDA's approval of vaccine made by four of the expected five manufacturers: CSL Ltd. of Australia, Switzerland's Novartis Vaccines, Sanofi Pasteur of France which produces flu shots at its Swiftwater, Pa., factory and Maryland-based MedImmune LLC, which makes the only nasal-spray flu vaccine.

London-based GlaxoSmithKline also was expected to supply vaccine. Sebelius said only that a fifth manufacturer's vaccine was expected to be approved soon, pending some final steps.

Getting licensing from the FDA means that the vaccine is made properly and meets specific manufacturing and quality standards.

What's the right dose? Figuring that out is the job of the National Institutes of Health, which last week announced studies showing that one dose appears to protect adults and that protection kicks in just eight to 10 days after the shot, faster than scientists had predicted.

Studies in children and pregnant women are continuing to settle on the right dose for those populations.

The H1N1 vaccine seems just as safe as the long-used regular flu vaccine, the FDA said, not a surprise as it's made the same way. Side effects include soreness or redness at the injection site, and some fever.

The government will keep a sharp eye for any very rare side effects. The last mass vaccination against a different swine flu, in 1976, was marred by reports of the paralyzing Guillain-Barre syndrome; scientists never proved whether that link was real or coincidence.