Broader use of hepatitis B virus vaccine: Efficacy in those who lost hepatitis B surface antigen during follow-up.
Dear Editor,

The article of hepatitis B vaccine in those who lost hepatitis B surface antigen during follow-up published recently in Hepatitis Monthly [1], described efficacy of HBV vaccine in chronic HBV patients who had been found negative for HBsAg and HBV DNA in sera. The manuscript was highlighted by an Editorial in same issue [2]. The manuscript dealt with a group of chronic HBV patients who were described as having occult HBV [3], with one major difference; usually occult HCV is defined as presence of low levels of HBV viremia in absence of detectable HBsAg but detectable anti-HBcAb, whereas in this manuscript [1] authors considered patients with undetectable HBsAg (with prior positive HBsAg) as well as undetectable HBV DNA levels (< 50 copies/mL of HBV DNA) with anti-HBe and anti-HBc antibodies. Thirty-four such patients and 52 control healthy individuals were vaccinated with three doses of HBV vaccine (Engerix-B, SmithKline Beecham); antibody levels were determined one month after last dose of vaccination. In control group, 87% of individuals developed protective levels of anti-HBs antibodies as has been reported earlier [4]. The major finding of manuscript was that in 24% of selected occult HBV patients, protective levels of anti-HBs antibodies developed. However, anti-HBs antibody levels were significantly lower than those of healthy individuals (mean ± SD: 68 ± 32.66 vs. 344.6 ± 38.99, p < 0.001). The authors suggested that the development of anti-HBs antibody may be a clue showing that they have protection and are less likely prone to develop chronic hepatitis, cirrhosis and hepatocellular This is an interesting study as it deals with HBV in patients whose disease outcome is not very clear. Also study suggests that role of HBV vaccine could be extended from prevention to therapeutic in certain cases of chronic HBV. However, sole appearance of anti-HBs antibodies cannot be taken to reflect viral clearance or non-progression to liver diseases. It has been shown recently that seroconversion from HBsAg positive to anti-HBs antibodies positive does not necessarily correlate to viral clearance [5]. In this respect, it is important to note that perhaps in patients with occult HBV and undetectable serum HBsAg, there may be no or reduced tolerance against HBsAg as compared to those with active chronic HBV with high serum levels of HBsAg and therefore, current HBV vaccine may be more effective in inducing anti-HBs antibodies. However, despite presence of anti-HBs antibodies, low levels of viral replication may continue in hepatocytes leading to further liver diseases such as cirrhosis, fibrosis and hepatocellular carcinoma. It is imperative that patients with positive response to HBV vaccine in current study [1], be followed for a longer duration to clearly examine role of induced anti-HBs antibodies in viral clearance or therapy of occult chronic HBV. As acknowledged by authors [1], liver biopsies could have provided more information regarding viral clearance in response to induction of anti-HBs antibodies. In addition, study needs to be expanded to a larger number of patients to make important conclusions. Nevertheless, paper represents an important study in examining role of current HBV vaccine in inducing protective anti-HBs antibodies in patients with occult HBV and may prove to be useful in expanding role of current HBV vaccine in therapy of occult chronic HBV.