The optimal interval for post-vaccination serological test in infants born to mothers with positive hepatitis B surface antigen.

Postvaccination serologic testing (PVST) is utilized to monitor the success or failure of vaccination against hepatitis B virus (HBV) infection in infants of hepatitis B surface antigen (HBsAg) positive mothers. This secondary analysis of 1255 infants of HBsAg-positive mothers at 7-14 months age included in two prospective studies aimed to determine the optimal interval for PVST after three hepatitis B vaccine doses. HBsAg and anti-HBs were quantitatively tested with microparticle enzyme immunoassay. The average PVST interval was 3.8 ± 2.2 months. Overall, 1.7% (21/1255) infants had anti-HBs <10 mIU/mL. The non-response rates were 1.6%, 1.1%, 0.9%, 0.7%, 1.1%, 0.7%, and 5.7% when PVST was performed at an interval of 1, 2, 3, 4, 5, 6, and 7-8 months after the third vaccine dose, respectively. Compared with 1 month of PVST interval, the non-response rate in infants who underwent PVST 7-8 months was significantly higher (χ2 = 4.616, P = .032). Anti-HBs titers were significantly declined in infants with medium responses when PVST was performed with longer intervals (χ2 = 27.592, P < .001), actually declined from interval of 6, and 7-8 months (Z = -3.177, P = .001 and Z = -3.715, P < .001), respectively. These results indicate that PVST may be performed at the age of 7-12 months for infants vaccinated on 0, 1, and 6-month schedule. To identify non-responders as early as possible, we suggest that PVST is performed at 7 months age or 1 month after the final vaccine dose.