Hepatitis B seroprevalence in Thailand: 12 years after hepatitis B vaccine integration into the national expanded programme on immunization

Abstract

Summaryobjectives To evaluate the impact of the universal hepatitis B (HB) vaccination programme on the prevalence of hepatitis B surface antigen (HBsAg) carriers and immunity to HB virus infection among children <18 years and to determine the HB seroprevalence in the Thai population.methods We enrolled people in four provinces, including Chiangrai, Udon Thani, Chonburi and Nakhon Si Thammarat to geographically represent populations in the North, Northeast, Center and South of the country respectively. Serology for HBsAg, anti-hepatitis B surface (anti-HBs), and antihepatitis B core (anti-HBc) was tested using ELISA commercial kits. In total, 6213 subjects aged 6 months to 60 years from the four provincial hospitals and two to three district hospitals of each participating province participated.results Overall HBsAg, anti-HBs, and anti-HBc seropositive rates amounted to 4%, 41.6% and 26.5% respectively. Of 2887 participants aged 6 months to 18 years, 2303 were born after (group I) and 584 prior to (group II) HB vaccine integration into the expanded programme on immunization of each participating province. The HBsAg seropositive rate was 0.7% among group I children and 4.3% among group II children. The prevalence rate of anti-HBc was 2.9% in group I and 15.8% in group II. In children under 18 years, the HBsAg carrier rate was 0.98% among complete vaccinees and 1.36% among participants without vaccination.conclusions This finding supports the efficacy of universal HB immunization in reducing the prevalence of HB infection in Thailand which is a highly endemic country.keywords seroprevalence, hepatitis B virus infection, hepatitis B vaccine, Thailand

Serological and molecular epidemiological outcomes after two decades of universal infant hepatitis B virus (HBV) vaccination in Nunavut, Canada

“…However, this may not be the case when comparing between endemic, high-risk and low-risk, non-endemic regions. Long-term follow-up studies are now being completed investigating antibody levels after initial infant vaccination in endemic regions, like Thailand and high-risk regions of Alaska [4,71]. However, these regions generally have slower antibody decay and more persistent levels over time.…”

“…After follow-up of universal infant vaccination within these regions, prevalence rates of HBsAg within vaccination age cohorts are now 0.7% and almost 0%, respectively [4,6].…”

“…As mentioned previously, the 'a' determinant is a highly conserved region of HBsAg, and contains the majority of epitopes that host anti-HBs antibodies will target. Mutations within the 'a' determinant have been observed in persons who have received the HBV vaccine in several regions of the world [4,[94][95][96]. The selective pressure may increase the emergence of surface mutants compared to wild-type.…”

“…Many regions and countries that were deemed high-risk for HBV infection have now run routine vaccination campaigns for almost three decades, and follow-up studies now show significantly reduced levels of chronic HBV infection within vaccination age cohorts in regions which include Thailand, Taiwan, and Alaska, amongst others [4][5][6][7].…”

Chronic hepatitis B in Asian women of childbearing age

“…Data from UNICEF from 2005 indicated that HBV vaccine coverage in infants ranged from 70 to 90% in most Asia-Pacific countries [45]. Unfortunately, the implementation of vaccination programs is reportedly inconsistent and access to these programs remains limited in some countries such as Myanmar, Bangladesh, and India as well as some rural areas, such as remote areas of China, where coverage is only 29% [2,6,13,45,46] (Table 2). Vaccine failure leading to vertical transmission remains a challenge.…”