Federal health officials are gearing up to persuade more Americans to get vaccinated against the flu this fall, in the aftermath of last year's pandemic that killed thousands nationwide, sickened millions, and frustrated many before petering out.

U.S. officials say they're using lessons learned from the H1N1 swine-flu pandemic, which erupted in April 2009, to speed the production and development of vaccine and to try to reach more people with shots. The government plans to plow nearly $2 billion into helping researchers and biotechnology companies develop new drugs, vaccines and equipment to shorten the six- to nine-month time frame currently needed to make a flu vaccine.

Last year's H1N1 vaccine took so long to produce that ample supplies became available only after the illness had peaked, and millions of doses went unused. That was after the disease killed nearly 13,000 people and sickened more than 60 million in the U.S. alone, according to estimates from the Centers for Disease Control and Prevention.

This year, the CDC is recommending flu vaccine for all Americans ages six months and older, except for people with egg allergies or certain other conditions. The new guidance expands a previous recommendation that had applied to about 85% of the U.S. population but didn't include healthy young adults—one of the groups hit hardest by the H1N1 pandemic virus.

This year's shot includes vaccinations against three strains of flu, including H1N1, that health officials think could be widespread this winter. They expect the H1N1 flu to return—possibly targeting the young again. At the same time, the CDC says, a new variant of a run-of-the-mill strain, known as H3N2, and an influenza B strain could also make many people sick. Both strains have circulated widely in the southern hemisphere's flu season in recent months, and the H3N2 strain can cause severe flu cases among the elderly.