Systematic reviews of the efficacy and effectiveness of influenza vaccination in infants, children and teenagers

Objectives. To identify and evaluate systematic reviews of the efficacy and effectiveness of influenza vaccination in healthy infants, children and teenagers. Material and methods. We searched for systematic reviews published before October 2006 in the following databases: MEDLINE, Cochrane Library Plus and Centre for Reviews and Dissemination Databases; a hand search was made of the references of selected reviews. Systematic reviews were included in the study if they evaluated the efficacy or effectiveness of influenza vaccines in healthy infants, children or teenagers in preventing influenza, influenza-like illnesses or other influenza-related illnesses in the individual or the community. Two reviewers independently applied inclusion and exclusion criteria to all the references found, assessed the quality of the reviews and extracted data from them. Results. The search retrieved 194 references, 7 of which were included in the review. 1. Efficacy and effectiveness in healthy infants, children and teenagers: a) efficacy in preventing influenza was 31-91% for the inactivated vaccine and 44-93% for the attenuated vaccine; b) effectiveness in preventing influenza-like illness was 10-67% for the inactivated vaccine and 11-52% for the attenuated vaccine; c) efficacy in preventing lower respiratory tract illness was 70% for the inactivated vaccine and 84% for the attenuated vaccine; d) efficacy in preventing otitis media ranged from -52% to 87% for the inactivated vaccine and 30-77% for the attenuated vaccine; e) efficacy in preventing school absenteeism was 54-86% for the inactivated vaccine and 49% for the attenuated vaccine. 2. Efficacy and effectiveness in vaccinated contacts: a) efficacy in preventing influenza ranged from -69% to 22% for the inactivated vaccine and 5% for the attenuated vaccine; b) the inactivated vaccine had null effectiveness in preventing influenza-like illness; c) its efficacy in preventing lower respiratory tract illness was 16-67%, compared with 8-18% for the attenuated vaccine. Conclusions. Influenza vaccines are efficacious and effective in preventing influenza, influenza-like illness, lower respiratory tract illness, otitis media and school absenteeism in healthy infants, children and teenagers. However, their efficacy and effectiveness are lower (or zero) in preventing these conditions in vaccinated contacts.