Healthcare workers (HCWs) are at increased risk of occupational exposure to hepatitis B virus (HBV) infection, even if they have received a complete immunization schedule of three doses of hepatitis B vaccine in infancy. According to our Hospital Immunization Program, Hepatitis B surface (anti – HBs) antibody serum levels were determined in all HCWs at the time of hospital admission in order to investigate the HBV immunity state. HCWs with low anti-HBs serum levels ( < 10 mIU/mL) usually received a booster dose of 20 µg/1 ml Engerix B ( GlaxoSmithKline Biologicals, Belgium) vaccine. However, due to a temporary shortage of the 20 µg Engerix B vaccine, we wondered if 10 µg/0,5 ml (pediatric dose) could be equally effective to elicit the immunogenicity in our HCWs. For this reason, we conducted a pilot study on forty homogeneous HCWs with a non-immune level of anti HBs antibody ( < 10 mIU/ml) who were previously vaccinated in infancy. Twenty HCWs (Group A) received a booster dose of Engerix B vaccine 10 µg/0,5 ml, and twenty HCWs (Group B) received the standard dose of 20 µg/1 ml of Engerix B vaccine. One month after the vaccination, the anti-HBs antibody serum levels in all participants in the study were determined. The results showed a significant increase in anti-HBs antibody serum levels both after 10 micrograms and 20 micrograms of Engerix B vaccine. All but two healthcare workers were immunized after their booster dose; no statistically significant difference was found in the mean of anti-HBs antibody serum levels between groups A and B. If confirmed in a large clinical trial, the use of 10 micrograms Engerix B booster dose in adults could represent a preferred choice in terms of cost efficacy, particularly in specific situations, for example in vaccination programs in low-income countries.