What kind of policy tool is the federal government using to encourage me to get the shot

Every time I walk near a drug store or doctor’s office during the Fall and Winter, I see a sign from the Centers for Disease Control telling me I should get a flu shot. What kind of policy tool is the federal government using to encourage me to get the shot? Even though I always get the shot, I hear that lot of people do not, which makes me mad. What would be the most effective tool for the government to use to get more people to get the flu shot and why? What would be some problems with that particular tool?