Intra-familial Transmission of Chronic Hepatitis B Infection: A Large Population-Based Cohort Study in Northern Iran.

Aim: The aim of this study was to investigate the intra-familial transmission of chronic hepatitis B (CHB) in Golestan province, that has the highest prevalence of CHB in Iran.
Methods: The Golestan Cohort Study (GCS) is a population-based prospective study of 50045 individuals, 40 years or older, initially set-up to study upper GI cancers in Northern Iran. In 2008, a baseline measurement of hepatitis B surface antigen (HBsAg) on the stored serum of all GCS participants identified 3505 HBsAg+ individuals. In 2011, we assessed HBV serological markers in 2590 initially HBsAg+ individuals and their first-degree relatives including spouses (1454) and children (3934).
Results: The median (IQR) age of spouses and children were 52 (12) and 25 (12) years respectively. Out of 5388 family members, 2393 (44.5%) had no HBV markers, indicating susceptibility to infection. Of these, 378 (15.8%) were fully-vaccinated children with no apparent response to primary immunization. HBsAg was positive in 2.2% (n = 33) of spouses and 8.2% (n = 325) of children (overall rate of 6.6%). HBcAb was positive in 761 (52.3%) and 914 (23%) spouses and children, respectively. The rate of spontaneous loss of HBsAg (HBsAg-, HBsAb+ and HbcAb+) was 41.3% and 13.9% in spouses and children, respectively. A higher rate of HBsAg+ children (10.2%) was found in families in which the mother was positive for HBsAg compared with families where the father was positive for HBsAg (6.3%) (P < 0.001). When both parents were positive for HBsAg, the rate of HBsAg positivity was high (23.5%, P < 0.001). Despite high virus exposure rates between spouses (52.6 %), the prevalence of HBsAg positivity among them was very low (2.3 %).
Conclusion: Sexual and parent-to-child transmission are important routes of CHB spread in this population from northern Iran despite the fact that 24 years have passed since the beginning of hepatitis B vaccination in infants. Low percentage of HBsAg positivity in spouses is related to high HBsAg clearance rate among them.
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