The Centers for Disease Control says this year the flu shot was 45 percent effective.
That means it reduced the risk of getting sick by nearly half.
Doctors say 90 children have died from the flu across the country this season, many of whom were not immunized.
That's the highest number in 15 years.
The North Dakota Department of Health says no one has died from the flu in the state this season, though 41 people have been hospitalized.