[Prevalence of hepatitis B and risk factors as motivation for vaccination campaign among adolescents]. / Prevalencia de infección por hepatitis B y factores de riesgo con motivo de una campaña de vacunación en adolescentes.

OBJECTIVES: To study the prevalence of viral Hepatitis B infection (VHB) among eighth-year EGB (basic) students; associated risk factors; and the prevalence of Hepatitis C (HC). DESIGN: A descriptive crossover study. SETTING: Eighth-year EGB students from 8 schools in Villaverde-Usera (Madrid). PARTICIPANTS: A sample of 262 individuals was used to calculate the prevalence of VHB infection (prevalence defined at 1.5%, precision = 0.015, confidence at 95% and 5% loss). MEASUREMENTS AND MAIN RESULTS: Variables were age, gender, alcohol, tattoos, drugs, family history of drugs, Hepatitis, exchanging syringes, razors, syringes, sexual relations, history of transfusions or surgery. These were obtained from a questionnaire filled in by the students themselves. The definitions were: chronic HB carrier: AgHBS+ in the blood; VHB infection: anti-HBc and/or anti-HBs positives; VHC infection: presence of anti-HC. 402 children answered the questionnaire. Serology was tested in 263 before the vaccination. Average age was 13.3 +/- 0.69. There were 52.8% males and 47.2% females. Prevalence of VHB infection was 2.28% (CI = 0.93-5.14), 6 cases. Prevalence of carriers was 0.38% (CI = 0.02-2.43; one case). There were no VHC positives. No links between VHB and risk practices could be demonstrated. CONCLUSIONS: 1) Low prevalence of VHB infection 2) The zero prevalence of VHC infection is lower than that in healthy donors.