NEW YORK (AP) — Health officials say the nasal spray version of the flu vaccine did not protect young children against swine flu last winter and might not work again this year.

Preliminary results from studies found that AstraZeneca's FluMist had little or no effect against swine flu in young kids. That was the most common bug making people sick last winter.

Why it didn't work isn't clear. The Centers for Disease Control and Prevention said it's possible the spray vaccine won't work again for swine flu this season.

But officials say the spray is still OK to use. Though the flu season is just getting started, early tracking suggests swine flu won't be a big player this year. Other strains are expected to be the major threat and the vaccine works against those.