Epidemiology and control of hepatitis B infection: a perspective from the Philippines, Asia.
The prevalence of chronic hepatitis B virus (HBV) infection in the Philippines, as indicated by hepatitis B surface antigen (HBsAg) positivity, ranges from 2% to 16.5%, with an average of 12% in a study of rural villagers. Although mother to child transmission is a major route of HBV infection, other routes (particularly child to child transmission) play an important part after the first year of life. In a study assessing the feasibility and effectiveness of incorporating hepatitis B vaccine into the national Expanded Programme on Immunisation, the coverage rate for fully immunised 1 year olds ranged from 80.9-84% and anti-HBs seroconversion rates ranged from 72-88%. In countries where HBV is not endemic, high risk groups include commercial sex workers (CSWs) and intravenous drug users (IVDUs), who generally have higher HBsAg positivity rates than the general population. In countries with a high HBV endemicity, carrier rates may be only slightly higher among CSWs, suggesting that other modes of transmission are more important in those regions. CSWs who are also IVDUs are at even greater risk. If HBV infection is to be controlled, innovative education and screening programmes are needed, together with the mass immunisation of neonates now started in many countries around the world.