Flu: Your Top Questions Answered

How you can protect yourself from getting sick this flu season.

Why was the vaccine so ineffective?

“The one thing about the flu that you can be sure, it’s really unpredictable,” Fauci said.

Though this year’s vaccine is not a strong match for the most prevalent strain of the flu, experts still recommended people get vaccinated because different strains of the virus will come into play as the season progresses. The shot may be a better match for the subtypes that dominate later in the year.

“There may be some level of cross-protection,” Dr. Richard Besser, ABC News chief health and medical editor, said. ” But we won’t know until March or so until we look back.”

Can I build immunity to a strain of the flu that’s been around before?

"Since then, everyone got sick or was vaccinated against that particular strain so you hardly see it going around," she said.

Immunity may not be life-long though, Strinchfield added. And even though having any kind of flu can help mitigate future bouts regardless of the subtype, some protection is not total protection.

Other than hand washing, what’s the best way to avoid the flu?