People should receive the vaccine every year as soon as it becomes available, said Weber. "It's important every year. This year it may be more important because anybody who didn't get H1N1 last year is susceptible to it, and since that was the first year H1N1 was around, many people, if not most people, are susceptible."

The vaccine is reformulated each year to provide protection against the virus strains that present the greatest public health threat for that year. People who contracted H1N1 last year may have a lower chance of contracting it again this year, but they should still receive the vaccine for protection against seasonal flu.

Adults need only one dose of the vaccine. Children 6 months to 8 years old may need two doses, depending on which vaccines they received last year.

The vaccine will be available at doctor's offices and at many pharmacies as both a nasal spray and as a shot. The shot is recommended for people younger than 2 or older than 49, and people with a suppressed immune system. The nasal spray is appropriate for most other healthy people.

SOURCE University of North Carolina at Chapel Hill