Surveillance for hepatitis B virus seroprevalence nearly 30 years after the implementation of a national vaccination program

Introduction Hepatitis B virus (HBV) infection is associated with cirrhosis and hepatocellular carcinoma. Vaccination is one aspect of public health policy aimed at eliminating HBV infection. After the implementation of an HBV vaccination program for newborns in Thailand, the estimated residual infection rate was 3.5%. However, that study was conducted in only 5,964 participants in seven provinces and only 22 years after the start of the campaign. This study aimed to evaluate the HBV seroprevalence rate in Thailand in larger sample size and a longer duration after program implementation using HBV surveillance. Methods This was a surveillance study conducted in 20 provinces in northeast Thailand The study period was between July 2010 and November 2019. Rates of HBV seroprevalence in each province and overall were calculated. Participants were divided into two groups: those vaccinated under the national campaign and those who were not. Participants aged 0.20 years were used as references, while other age groups (intervals of 10 years) were comparators. Residual HBV seroprevalence after the vaccination program was calculated with odds ratio for HBV seroprevalence in each age group. Results There were 31,855 subjects who participated in the project. Of those, 1,805 (5.7%) had HBV. The HBV seroprevalence rate in the national HBV vaccination group was significantly lower than that in those not vaccinated under the national program (1.0% vs 5.9%; p<0.001). Seroprevalence was 1.0% in participants <= 20 years of age. Participants 31.40 years of age had the highest odds ratio (10.41), followed those 21.30 years of age (7.42). Conclusions This real-world surveillance study showed that residual HBV infection was 1.0% after nearly 30 years of nationwide HBV vaccination.