The risk factors of transmission after the implementation of the routine immunization among children exposed to HBV infected mothers in a developing area in northwest China.

We aimed to evaluate the present situation and possible risk factors of HBV transmission after the implementation of the routine immunization among children exposed to HBV infected mothers in a developing area in northwest China. Two hundred and twenty one HBsAg carrier mothers and 247 children born to them were finally recruited in Wuwei city, Gangsu province, China in 2010. Serum samples were taken from those HBsAg carrier mothers and their children. Children who had detectable HBsAg or HBV DNA were considered to be HBV infection. Conditional logistic regression model was used to identify potential risk factors of HBV mother-to-child transmission. Of the 247 children born to HBsAg carrier mothers, 8 (3.24%) were HBsAg positive, 15 (6.07%) were HBV DNA positive. The rate of HBV mother-to-child transmission was 7.29% (18/247). The univariate analysis and multivariate analysis showed that maternal HBV DNA positive (OR=4.83, 95% CI: 1.38-16.98, p=0.0140), the delayed injection of the first dose of HBV vaccine after premature birth (OR=9.73, 95% CI: 1.78-53.21, p=0.0087) and the missing use of HBV vaccine (OR=8.29, 95% CI: 1.42-48.23, p=0.0186) were significantly associated with an increased risk for HBV mother-to-child transmission. The rate of HBV infection of the children received HBV vaccine and HBIG together after birth (2.56%, 4/156) was lower than those children received HBV vaccine alone (11.39%, 9/79) (χ(2)=7.83, p=0.0052). In conclusion, the rate of mother-to-child transmission of HBV was still high in the northwest of China. Besides the positivity of maternal HBV DNA and the missing of HBV vaccination after birth, the delayed injection of the first dose of HBV vaccine after premature birth was also a possible independent risk factor for HBV mother-to-child transmission. The HBV prevention and treatment guidelines should make it clear that all of the new born infants need to receive HBV vaccine injection after birth in 24 h, including the premature infants.