The purpose of this study is to determine whether inactivated influenza vaccines are effective to protect school children and their households from getting influenza infection and further prevent student's absenteeism.

School children were found to be the possible spreaders of the influenza. The successful prevention measure on school children was crucial for controlling the epidemic. In Taiwan, the national influenza immunization program on the grade 1-2 students started in winter, 2007. In this intervention study, the two study townships with 27 schools were included as our study population. The three time questionnaires were issued for collecting the health status of the children during the influenza season. The information on the vaccines' safety was also collected after the vaccination. The community collaborative clinics were responsible for taking the specimens.

Inclusion Criteria:

• All elementary and junior high school students living in Shinwu and Guanyin townships were eligible to be enrolled into this study
• Agreed inform consent to participate in this study
• Complete three times questionaire follow-up

Exclusion Criteria:

• One junior high school in Shinwu township because it had both high school and junior high school