WASHINGTON (AP) -- Time to get your flu vaccine. And remember: Last year's shot won't protect you this year.

Federal health authorities said Thursday that this year's vaccine contains protection against two different strains that have begun circling the globe. And just because flu was mild last winter, doesn't mean it won't bounce back with its usual ferocity this winter.

With 135 million doses expected, there's plenty of vaccine to go around.

Flu vaccination is recommended for virtually everyone older than 6 months of age. But the government says just 42 percent of Americans were immunized last year.

The good news is that three-quarters of babies and toddlers were vaccinated. But even though people 65 and older also are at very high risk, just two-thirds were vaccinated.