Absence of maternal antibodies to hepatitis B core antigen and HBV vertical transmission: one case of infection notwithstanding passive-active prophylaxis.

We report the case of a newborn of an HBsAg carrier mother who was infected by vertical transmission and developed a subclinical hepatitis B at four months of age, notwithstanding the passive-active prophylaxis performed right after birth. The mother's HBV marker status was: HBsAg positive, HBeAg positive, anti-HBc IgM positive at low titer, anti-HBc IgG negative, anti-HBs negative, anti-HBe negative. It is assumed that the absence of anti-HBC antibodies might have favoured, perhaps in utero, the HBV infection whose antigenic expression was subsequently delayed by HBIg administered at birth. These findings suggest that the positivity for anti-HBc IgM must be considered an additional marker of maternal infectivity especially in the absence of anti-HBc IgG antibodies.