Anti-HBs testing should not be performed before 9 months of age in infants of mothers with hepatitis B infection who received hepatitis B immunoglobulin at birth

We read with great interest the paper by Osiowy et al (1) titled “The management of chronic hepatitis B: 2025 Guidelines update from the Canadian Association for the Study of the Liver and Association of Medical Microbiology and Infectious Disease Canada.” In their article, Osiowy et al aimed to provide guidance in daily practice for the management of chronic hepatitis B. We agree with all the views presented in this article. However, we would like to draw attention to an important situation related to the printing error regarding the timing of post-vaccination testing. In the part “Recommendations for HBV management in pregnancy,” the recommended timing of post-vaccination testing was miswritten in the text as “Infants should be tested for HBsAg and anti-HBs between one and four months after the last dose of vaccine (by one year of age) to confirm that they are uninfected and immune to HBV.” This means that, considering that the last dose of vaccine will be given when the infant is 6 months of age, the hepatitis B surface antibody (anti-HBs) test should be 1 to 4 months later; that is, when the infant is between 7 and 10 months of age. However, the recommended timing of post-vaccination testing for infants of HBsAg-positive mothers is when they reach 9 to 15 months of age, as proposed by the American Association for the Study of Liver Diseases’ (AASLD’) 2018 hepatitis B guidance (2) because hepatitis B immunoglobulin (HBIG) given at birth contains anti-HBs. If the infants are tested for anti-HBs before they reach 9 months of age, there will be the possibility of passive anti-HBs detection from the HBIG administered at birth. Since the aim is to prevent passive anti-HBs detection and to maximize the likelihood of detecting late HBV infection, infants who received an immunoprophylaxis with HBIG and HBV vaccine at birth should not be tested for anti-HBs before they are 9 months of age (3).

We think that if the timing of post-vaccination testing is when the infant is 9 to 15 months of age, as recommended in the AASLD 2018 hepatitis B guidance (2), it will prevent any possible confusion in daily practice.