Impact of hepatitis B vaccination programs in Vietnam evaluated by estimating HBsAg prevalence

Abstract

Background: Vietnam introduced a 3-dose hepatitis B (HBV) immunization program comprising 1 dose immediately after birth and 2 or 3 in infancy in the past 20 years, but the impact of the vaccine has not been systematically evaluated. Thus, we conducted this survey aiming to estimate the age-specific chronic HBV prevalence in the general population and to evaluate HBV immunization effectiveness. Methods: Population-based, four-stage cluster sampling was used in the South Central Coast region of Vietnam. The point-of-care Determine rapid test was used to assess hepatitis B surface antigen (HBsAg) positivity. Results: A total of 2,075 samples were included in the study. HBsAg prevalence was significantly higher among adults aged 20–39 years than in the population aged 1–19 years (8.0% [95% confidence interval 5.0–12.0] vs. 2.0% [95% confidence interval 1.0–6.0], p<0.01). HBsAg prevalence decreased after implementation of the 3-dose vaccination schedule during infancy from 1997 to 2002, whereas the change in prevalence after implementation of the birth dosing was not significant. A slight increase in HBsAg prevalence was observed for the cohort born in 2011, 2012, and 2013, when there was a vaccine shortage and media reports of immunization resistance. Conclusions: This is the first population-based assessment of the introduction of the HBV vaccine in Vietnam performed by estimating the HBsAg prevalence across a wide range of ages. The results showed that the HBV immunization policy effectively reduces HBsAg prevalence in general, although birth dosing of the vaccine and low immunization coverage should be carefully monitored.

Keywords

• Hepatitis B surface Antigen
• Seroprevalence survey
• Cluster sampling
• Immunization
• Vietnam