Federal health officials are facing questioning about why this year’s flu vaccine isn’t giving good protection against the winter menace.

This is a particularly bad flu season, and one reason is that the most common flu strain isn’t a good match to this year’s vaccine. Lawmakers on Tuesday asked why the Centers for Disease Control and Prevention didn’t act months ago when concerns first arose to create a better-matched vaccine.

CDC immunization chief Dr. Anne Schuchat says it wasn’t possible to change course. While CDC first noticed a slight change in that strain last March, by the time the shift had become common in September, it was too late.

At the same, lawmakers urged that kids be vaccinated against measles amid an outbreak that has sickened more than 100.

(AP)