Long-term effectiveness of vaccination for prevention of hepatitis B virus mother-to-child transmission in Yunnan, China.

In 2011, a study on preventing mother-to-child transmission (PMTCT) of Hepatitis B virus (HBV) was conducted in Yunan province, China, and a child cohort was formed to assess PMTCT's long-term effectiveness. In 2022, subjects were randomly selected from this cohort to investigate HBV infection status and anti-HBs antibody levels among the HBsAg-negative children from the 2011 PMTCT group. HBV markers (HBsAg, anti-HBs, anti-HBc) and genomic information were detected, and risk factors for HBV breakthrough infection were analyzed. In total, 235 children were enrolled. HBsAg and anti-HBc positive rates were 1.7 % (4/235) and 5.96 % (14/235). HBsAg prevalence did not substantially increase, but four new HBV carriers were identified, with S gene sequences highly homologous to their parents'. The anti-HBs positive rate dropped significantly (from 86.38 % in 2011 to 58.30 % in 2022, χ2 = 46.32, P < 0.001), yet it went up among those who had booster vaccinations (93.2 % in 2022; 78.0 % in 2011), though antibody levels did not increase. Phylogenetic analysis confirmed the possible intrafamilial HBV transmission and no significant important mutations. Univariate and logistic regression analyses indicated that maternal HBeAg positivity were a major risk factors for children's HBV breakthrough infection (OR = 4.23, 95 % CI: 1.17-15.25). In conclusion, the positive rate and levels of anti-HBs antibodies have declined over time, but infection rates has not substantially increased. Children of HBsAg-positive parents remained at high risk of HBV breakthrough infection. Even with successful PMTCT, measures should be taken to maintain their immunity and reduce direct HBV exposure.