Hepatitis B surface antigen and antibody positivity among women of childbearing age after three decades of universal vaccination in South Korea.

OBJECTIVES: We estimated the impact of universal hepatitis B immunization using 18-year data of women who are of childbearing age in South Korea. METHODS: We used hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) data of 145,993 women aged 20-49 years during 2001-2018 at the Gangnam CHA Medical Center. Annual prevalences of HBsAg and anti-HBs positivity were calculated and tested for linear trend. We conducted age-period-cohort (APC) analysis to obtain period and cohort effect. RESULTS: Overall proportion of HBsAg positivity was 3.5% (n = 5050) and anti-HBs positivity was 75.3% (n = 109,907) during the study period. HBsAg positivity percentage decreased from 5.1% in 2001 to 2.5% in 2018 (P < 0.001) while anti-HBs positivity increased from 59.9% to 75.8% (P = 0.002). Average annual percent change of HBsAg positivity was -5.9% (95% confidence interval (CI): -6.9%, -4.8%). The period and cohort RR curve identified a consistent decrease in HBsAg positivity over time and across generations. CONCLUSIONS: We observed a concurrent decrease in HBsAg and an increase in anti-HBs seropositivity among Korean women of childbearing age, implicating success in preventing vertical transmission.