Absence of anti-hepatitis B surface antibody after vaccination does not necessarily mean absence of immune response

A small number of subjects vaccinated against hepatitis B do not produce an ti-hepatitis B surface (HBs) antibody levels detectable by commercial assay s. Others lose detectable anti-HBs at some time after vaccination. The abse nce of clinical hepatitis despite potential exposure to hepatitis B virus ( HBV) in both kinds of subjects suggests that they might be protected by low antibody levels. However, besides anti-HBs, T helper response and memory c ells which may be induced by the vaccine are certainly also important for i mmunity against HBV. In the present study, samples from vaccinated subjects , found to be anti-HBs negative in an initial assay, subsequently showed po sitive results in, respectively, 25%, 36% and 38% of the cases, when a seco nd, third and fourth assay was used. In addition, 360 samples from "nonresp onders" and from vaccinees who had lost anti-HBs, the reactivity of which w as under the enzyme-linked immunoassay-cut-off value were compared to that of nonvaccinated controls. The absorbances were found to be significantly h igher in the nonresponders (0.038) and in the vaccinees having lost anti-HB s (0.041), than in the controls (0.025). Such findings contribute to explai ning why so-called nonresponders as well as vaccinees who have lost anti-HB s nevertheless appear to be protected.