The First Assessments of Pediatric HBV Immunization Coverage in Mauritania and Persistence of Antibody Titers Post Infant Immunizations.

Background: The Hepatitis B virus (HBV) vaccine is used worldwide as an efficient tool to prevent the occurrence of chronic HBV infection and the subsequent liver disease. However, despite decades of vaccination campaigns, millions of new infections are still reported every year. Here, we aimed to assess the nationwide HBV vaccination coverage in Mauritania as well as the presence of protective levels of the antibodies against HBV surface antigen (HBsAb) following vaccination in a sample of children immunized as infants.

Methods: To evaluate the frequency of fully vaccinated and seroprotected children in Mauritania, a prospective serological study was conducted in the capital. First, we evaluated the pediatric HBV vaccine coverage in Mauritania between 2015 and 2020. Then, we examined the level of antibodies against HBV surface antigen (HBsAb) in 185 fully vaccinated children (aged 9 months to 12 years) by ELISA using the VIDAS hepatitis panel for Minividas (Biomerieux). These vaccinated children were sampled in 2014 or 2021.

Results: In Mauritania, between 2016 and 2019, more than 85% of children received the complete HBV vaccine regimen. While 93% of immunized children between 0 and 23 months displayed HBsAb titer >10 IU/L, the frequency of children with similar titers decreased to 63, 58 and 29% in children aged between 24-47, 48-59 and 60-144 months, respectively.

Conclusions: A marked reduction in the frequency of HBsAb titer was observed with time, indicating that HBsAb titer usefulness as marker of protection is short lived and prompting the need for more accurate biomarkers predictive of long-term protection.