We’re thinking of using Twinrix (combination HepA-HepB) and we’re wondering whether we can use it for doses #1 and #3 only and use single antigen hepatitis B vaccine for dose #2?

No. Twinrix contains 50% less hepatitis A antigen component than Havrix, GSK’s monovalent hepatitis A vaccine [720 vs. 1440 El. U.], so the patient would not receive the recommended dose of hepatitis A vaccine antigen. For this reason, 3 doses of Twinrix must comprise the series.