WASHINGTON – First there was too little swine flu vaccine. Now could there be way too much?

This week will tell. Get ready for a huge flu-shot push as health officials try to rekindle interest in protection against this new influenza strain that, despite plummeting cases, still is threatening lives — even as they reassess just how much more vaccine needs to be shipped.

There’s finally plenty of vaccine — 136 million doses and counting — against what scientists call the 2009 H1N1 flu strain. No more standing in long lines at the health department. CVS drugstores have so much the chain is touting vaccine in national radio and TV ads. Competitor Walgreens got more than 50,000 takers in a single day last week.

Monday, children younger than 10 began rolling up their sleeves for a second time in Rhode Island schools. The state has attracted acclaim for vaccinating three-quarters of its students, and now is starting Round 2 — the second dose required to protect kids that young.

And flu-shot drives for all ages are scheduled around the country for what’s officially dubbed National Influenza Vaccination Week — in hopes of preventing a possible third wave of the epidemic later this winter.

How much demand this week brings will put the U.S. at a critical juncture: When is it time to halt the bottling of vaccine, so that too many unused doses don’t go to waste?

Australia’s CSL Ltd. revealed Monday that U.S. officials have cut by more than half the amount it was supposed to ship here, 14 million doses instead of 36 million. The nation’s largest suppliers — Sanofi-Pasteur, Novartis and MedImmune — told The Associated Press that their orders were unchanged so far. But other countries already are looking to unload leftovers.

U.S. officials say they’re deliberately delaying that decision.

“The danger is in turning off the spigot before we really know what the winter flu season looks like, what the demand is,” Health and Human Services Secretary Kathleen Sebelius told the AP. “As long as there is demand, the good news is we will have a supply.”

More than 60 million people are thought to have been vaccinated so far, and the U.S. is flush enough that Sebelius said the long-promised donation of 25 million doses to developing countries is ready to ship.

Flu vaccine is a balancing act. Every year the nation throws away millions of leftover shots. They actually last well beyond their June 30 expiration dates. But because each year’s flu vaccine is a mix of three different strains, with at least one change to the recipe almost every year, leftovers are destroyed to avoid confusion.

This year is different. The government ordered 250 million doses of swine flu vaccine to be made in bulk, but just over half of it to be put into vials ready to go into people’s arms or up their noses. That was a strategic move, because vaccine stored in bulk lasts far longer — meaning leftover bulk antigen could be stored and used as an ingredient in next fall’s flu vaccine if it looks like it will be needed again.

In fact, nasal-spray vaccine maker MedImmune already has frozen bulk supplies in anticipation of doing just that.

While U.S. cases have plummeted from a peak in October, one state — Alabama — is experiencing widespread infections and the Centers for Disease Control and Prevention says there’s still more flu going around now than is usual for early January, all of it the new strain. Moreover, the World Health Organization says swine flu is widespread in much of the world, particularly Egypt and India.

Because the virus hasn’t mutated yet, specialists expect this H1N1 strain to be designated part of next fall’s all-in-one vaccine when regulators meet in February to set the recipe.

The bulk purchasing means “I don’t see the U.S. wasting any vaccine here,” says Dr. Michael Osterholm, a University of Minnesota expert on pandemic preparations.

But, “we’re far from done yet,” adds Osterholm, who worries that people will put off getting a swine flu vaccination unless cases start to rebound. “If we had to try to put through 20, 30 million people in a couple of weeks because suddenly the next wave takes off, it would still be a scramble.”

Indeed, in the flu pandemic of 1957, the government gave an all-clear after a fall wave of disease, only to see deaths increase again later in the winter.

Still, demand is falling fast. Last week, New York’s state health department had to send two trucks to pick up unused vaccine from counties with leftovers they couldn’t store.

And Sebelius got a mixed reaction when she kicked off vaccination week Sunday at a prominent Washington church that will hold its own inoculation clinic next weekend.

“I’m a little leery,” said Dellareesa M. Bank of Silver Spring, Md., who said she’s unlikely to be vaccinated at Nineteenth Street Baptist Church despite her pastor’s pledge to be.

But Karyn Sanders of Upper Marlboro, Md., was persuaded.

“It made me say, ‘Oh, well, there’s still a threat,’” said Sanders, who plans to bring her two children in for vaccination.

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EDITOR’s NOTE — Lauran Neergaard covers health and medical issues for The Associated Press in Washington. AP writers Natasha Metzler in Washington and Mike Stobbe in Atlanta contributed to this report.