Illinois Department of Public Health director Dr. Damon Arnold says it's important for those who can receive flu shots to get vaccinated to protect others who can't get vaccinations, like those who are allergic or babies younger than six months old.
Department officials say the vaccination is available at local health departments and some doctor's offices, health clinics, hospitals and pharmacies.
The vaccine is available as a shot or as nasal spray.
Public health experts say influenza is mainly spread when people don't properly cover coughs and sneezes. They say holiday travel and gatherings increase the opportunity for influenza to spread.