To the Editor: Wiseman and colleagues reported the 9-month virological follow-up of babies born to pregnant women attending urban antenatal clinics who tested positive for hepatitis B surface antigen (HBsAg).1 Evaluation of outcomes is vital to determine implementation and effectiveness of current policy.

The authors state that hepatitis B immunoglobulin (HBIG) and hepatitis B virus (HBV) vaccine were delivered within 12 hours of birth to all infants of HBsAg-positive mothers. Nine months after birth, transmission was documented in only four infants, all of whom were born to mothers who were positive for hepatitis B “e” antigen (HBeAg) and had very high HBV DNA levels (> 108 copies/mL). Yet one of the four infected infants had inadvertently not received the “routinely offered” HBIG. Whether any other babies (even if not infected) also failed to receive timely active and passive immunisation was not explicitly reported.

The other three infected infants completed HBIG injection and HBV vaccination according to the “recommended schedule”. Given that the Australian immunisation handbook states that

the exact time is unclear. Potentially, a delay of many hours to many days could occur. Yet, for all infectious diseases for which post-exposure prophylaxis is given, administration as soon as possible after exposure is universally recommended to prevent transmission.3 For babies born to known HBeAg-positive mothers, particular effort is warranted to ensure that they receive HBIG and HBV vaccine immediately after delivery, and certainly within hours of birth.

There are many difficulties in achieving high rates of follow-up in this group, and only 66% of babies in the study by Wiseman and colleagues had virological follow-up results available. Unfortunately, the authors did not make the important distinction between babies lost to follow-up and those who were not yet 9 months old at the time of follow-up. This is in spite of the fact that the study included many South-East Asian women, who have markers of high HBV replication and whose follow-up is suboptimal.4

Evaluation of HBV vaccination policy requires that studies report fully on outcomes, including loss to follow-up. Also, given that delay in administration of HBIG and HBV vaccine after delivery may be a critical source of variation in outcome, future studies should specifically report this information separately for all births to HBsAg- and HBeAg-positive mothers, and for any cases in which transmission does occur.

In reply: We thank Thompson for her comments.

We endeavoured to contact women by phone, by letter, or through their local doctor (if known). With respect to the 69 infants lost to follow-up, five of the mothers declined assessment, four had moved interstate or overseas with their families, five had infants who had not reached 9 months of age, and the remaining mothers were uncontactable. Follow-up of a cohort of this kind is difficult, for reasons that include language barriers and high rates of mobility. Furthermore, at the time of the study, testing the babies was not standard practice and not enthusiastically received by all mothers. We are not a public health unit and are not resourced to pursue follow-up beyond the measures described. Nevertheless, through strong engagement with the mothers, who were referred on the basis of their hepatitis B virus (HBV) infection, we achieved follow-up for a large number of babies. The data stand as valuable but not perfect.

As mentioned in our article,1 vaccination practice for babies born to infected mothers is for hepatitis B immunoglobulin and the first HBV vaccine dose to be given (in opposite thighs) within 12 hours of birth. The babies’ vaccination records were checked by consulting the “blue book”, a standardised medical record for infants, and, for those infected, by cross-checking with the hospital medication chart.