ATLANTA (AP) – Get ready to roll up your sleeve three times for flu shots this fall.

That's right, three times. This year's flu season is shaping up to be a very different one. Most people will need one shot for the regular seasonal flu and probably two others to protect against the new swine flu.

Experts suggest you get that first shot as early as this month – if you can find it.

"We'd like to get to Job 1 and get most of it done," said Dr. William Schaffner, a Vanderbilt University flu expert, referring to seasonal flu vaccinations.

"Get it done before we start to tackle Job 2," the more complex task of swine flu vaccinations, he added.

The five vaccine manufacturers that supply the United States are finishing up production of seasonal flu vaccine earlier than usual. Health officials say they expect about half of the more than 120 million doses of seasonal vaccine to be available by the end of this month. Most of the rest are due out by the end of September. Some manufacturers report that distributors are quickly buying up supplies.

Those five companies – including one that makes a nasal spray version of flu vaccine – are the same ones making the new swine flu vaccine. They are on track to start delivering the first batches of that in September, but the bulk of it isn't expected until late October or November, health officials say.

That's sparked questions about how all this is going to work. Officials want to get as many people as possible vaccinated against both forms of flu, but a lot of that depends on consumers and how many trips they'll be willing to make to get shots.

Why can't you get one shot for all – or maybe just two?

The reasons have to do with logistics and caution.

Scientists believe the swine flu vaccine will be most effective if given in two doses, about three weeks apart, although testing is still under way to check that.

Combining swine flu and seasonal flu in one shot is theoretically possible, but it was too late to try it this year. Decisions were made last winter about what flu strains to use in this year's seasonal vaccine, and production was too far along by the time swine flu hit in April to alter the formula.

So seasonal flu and swine flu will have to be given as separate doses, even if it's during the same appointment.

But it's not a matter of just giving both to whoever comes in. Supplies are expected to be limited, so the federal Centers for Disease Control and Prevention has two different lists for who should be first to get the seasonal flu shot and who should be first to get the swine flu shot.