Part of the reason for a rise in people coming down with the flu this year might be the flu shot being largely ineffective. The Centers of Disease Control says the flu shot came in at 23 percent. In recent history the flu shot has been between 10 and 60 percent effective. Doctors have to try to match the flu shot to the flu strains going around but that is not always easy. The CDC called the current flu season as “moderately severe.”