Progress Towards Elimination: Hepatitis B and C Among Children and Young Adults in Rural Mongolia.

Mongolia is a global hotspot for viral hepatitis, with estimated rates of chronic hepatitis B (HBV) of 11% and hepatitis C (HCV) of 8.5% among adults. Data on infections among children and young adults and the impact of vaccination against HBV are less clear. In 2018 and 2019, 3800 children and young adults aged 25 and younger from all provinces in Mongolia apart from Ulaanbaatar and Tuv were tested for hepatitis B surface antigen (HBsAg), hepatitis B core antibody (HBcAb), hepatitis B surface antibody (HBsAb), hepatitis C antibody (HCVAb) and hepatitis D antibody (HDVAb). HBsAg positive and serologically positive samples were evaluated for viremia. Risk factors for viral infection were assessed using a questionnaire. In total, 1.34% (51/3800) of participants were HBsAg positive. HBsAg positivity among 20-24 year-olds (5.4%) was 8.8 times higher than in those aged < 19 (0.6%). The prevalence of previous HBV infection was 6.7%. HBsAb without indication of prior infection, reflecting vaccination, was detected in 24.2%, declining with increasing age. Among HBsAg-positive samples, 86% (44/51) had detectable HBV-DNA and 27.45% tested positive for HDVAb (14/51). Only a family history of viral hepatitis was identified as a risk factor. A total of 0.31% (12/3800) of all participants were HCVAb positive. For HBV, the data generally show a much lower infection rate, especially among those born since 1998. Likely, the main reason for this decline is the infant vaccinations against HBV. For HCV, the low number of cases confirms that mostly older Mongolians are affected by HCV.