To explore the significance of monitoring hepatitis B surface antibody (HBsAb) level in infants of mothers with chronic hepatitis B virus (HBV) infection and to assess the safety of breastfeeding.

Total of 213 infants of mothers with HBV infection from December 2017 to December 2018 in Beijing Ditan Hospital, Capital Medical University were enrolled, who received immunization program of HBV mother-to-child transmission blockade. The measures of HBV mother-to-child transmission blockade included injection of hepatitis B virus immune globulin (100 IU) and recombinant hepatitis B virus vaccine (10 μg) at different sites within 24 hours after birth, and immunization with hepatitis B virus vaccine (10 μg) at one month and six months, respectively. The levels of HBsAb and HBV DNA of venous blood were detected among the enrolled infants within 24 hours, 42 days, 3 months, 7 months and 12 months after birth. The levels of HBsAb at different time points were analyzed by non-parametric tests for Kruskal-Wallis H (K) and rank-sum test; the ratio of non/low response to hepatitis B vaccine immunity at different time points were compared by Chi-square test.

The average gestational age of 213 infants was (38.72 ± 1.20) weeks, the mean birth weight was (3.29 ± 0.39) kg, there were 151 (70.89%) cases with natural birth, 62 (29.11%) cases with cesarean section, 75 (35.21%) cases with positive maternal hepatitis B virus e antigen (HBeAg), 90 (42.25%) cases with HBV DNA load > 2 × 10⁵ IU/ml at 28 weeks, and 109 (51.17%) cases underwent antiviral treatment during pregnancy. The levels of HBsAb at birth, 42 days, 3 months, 7 months and 12 months after birth were 0.5 (0.31, 0.92) mIU/ml, 247.76 (232.99, 294.49) mIU/ml, 163.3 (105.85, 311.59) mIU/ml, 1 000 (887.56, 1 000) mIU/ml and 239.99 (106.76, 515.90) mIU/ml, respectively. The overall difference between each time point was significantly different (Z = 308.51, P < 0.001); and each time point was statistically different from the previous time point (42 days vs. at birth: Z =-7.09, P < 0.001, 3 month vs. 42 d: Z =-3.23, P = 0.001, 7 months vs. 3 months: Z =-14.32, P < 0.001; 12 months vs. 7 months: Z =-12.00, P < 0.001). The rates of non/low response to hepatitis B virus vaccine at 42 days, 3 months, 7 months and 12 months after birth were 1.88% (4/213), 42.72% (91/213), 3.76% (8/213) and 24.41% (52/213), respectively, the overall difference between each time point was significantly different (χ² = 159.58, P < 0.001), the difference at each time point was statistically significant from the previous time point (3 months vs. 42 days: χ² = 102.54, P < 0.001, 7 months vs. 3 months: χ² = 90.65, P < 0.001; 12 months vs. 7 months: χ² = 37.56, P < 0.001). Two infants at 3 months and one infant at 7 months with HBV DNA positive all had low response to hepatitis B virus vaccine. The ratio of non/low response to hepatitis B virus vaccine immunity between infants with HBV DNA positive and with HBV DNA lower than the lowest limit at 3 months and 7 months old were significantly different (Fisher’s exact probability test: P = 0.18, 0.24), which may be related to the small sample size.

HBsAb fluctuates greatly during breastfeeding of HBV-infected mother’s infants, and the rates of non/low-response status at 3 months and 12 months after birth were high, and monitoring of HBsAb levels should be strengthened to ensure the safety of breastfeeding.