Twenty-five children in Fallsburg Elementary School (with a population of 60 pupils) received their immunization against whooping cough to protect the school's student population. In your role as health officer, you collected the documentation from parents on the first day of school. You found that 25 students had received their immunization against the disease. You have been asked to explain some basic epidemiologic concepts to the parents who did not have their children immunized.
You have been tasked to do the following:
Define the term population at risk and indicate which of the elementary students are not at risk. Also describe the difference between incidence and prevalence.