Neonatal Vaccination Against Hepatitis B in Africa - Sero-survey in Senegal

Chronic infection with hepatitis B virus (HBV) is a leading cause of death in adults in sub-Saharan Africa (SSA). Each year, about 61,000 people are estimated to die of hepatocellular carcinoma (HCC) or cirrhosis secondary to chronic infection with HBV. Prior to the introduction of the hepatitis B vaccine, main modes of transmission in SSA were perinatal transmission from mother-to-child (MTCT) (10%) and horizontal transmission during early childhood (90%). MTCT occurs through contact with maternal fluids during passage through the birth cana; transplacental transmission and transmission through breastfeeding are rare. Despite a relatively low frequency of perinatal transmission in SSA, prevention of this type of transmission is important, because this mode of transmission results in higher risk of becoming chronic HBV carriers, and developing chronic liver disease, including HCC, than horizontal transmission. In 2009, WHO recommended the administration of hepatitis B vaccination to all newborns within 24 hours of birth to prevent perinatal and early transmissions. In Senegal, the government introduced the monovalent vaccine that can be used within 24 hours after birth in the Expanded Program on Immunization (EPI) in March 2016. It is in this context that the NeoVac study started in 2016 in Senegal, Burkina Faso and Madagascar. The general objective is to develop a long-term strategy adapted to the local context to vaccinate newborns against hepatitis B in the first 24 hours of life. The NeoVac 1, a population-based epidemiological survey to estimate the coverage of this newly introduced monovalent hepatitis B vaccine started in Senegal in 2018. Here, we present a study protocol for a sero-epidemiological study of pairs of children aged 9 to 12 months and their mothers, identified through the demographic study, to assess the impact of monovalent vaccine introduced by the national program for prevention of mother-to-child transmission in Senegal. We will also assess the diagnostic performance of loop-mediated isothermal amplification assay (LAMP) to identify people with high viral replication (HBV DNA ≥200,000 IU/ml), compared to a conventional reference test (PCR).