Vaccinating schoolchildren against influenza would prevent the disease among non-vaccinated household members.

Children and adolescents play an important role in sustaining the transmission of influenza. Moreover, with the occurrence of influenza in children, there are important socioeconomic consequences to families affected by the disease, related to absenteeism, expenditure on health services and medication use. This study presents an evaluation of direct and indirect effectiveness of influenza vaccination in school age children and their unvaccinated household contacts. It was conducted in 2009, in Sao Paulo - Brazil, through a randomized double-blind community trial, with six months of follow up. For the evaluation of vaccine effectiveness, the influenza vaccine was used for the experimental group, and meningitis conjugate and varicella vaccines for the control group. After vaccination, the volunteers and their families were followed for six months, in order to identify cases of acute respiratory infection (ARI) and to collect biological samples for testing with RT-PCR for diagnosis of influenza.

Inclusion Criteria:

• older than six years of age;
• live in the study area;
• parent consent to participate, by signing the Informed Consent Form;
• no history of anaphilaxis or hipersensitivity to eggs or eggs proteins;
• no history no history anaphilaxis or hipersensitivity to any substances;
• no acute disease at the moment of vaccination
• no use of immunesupressant drugs;
• not have received any other vaccine in the previous six months;
• no participation in other clinical trial in the previous six months.

Exclusion Criteria:

• Any condition above mentioned.