Background and Aims The objective of this study was to determine whether use of a longer (1 in.) rather than astandard (5/8 in.) needle used for macrosomic neonates (birthweight over 4000 g) may affect antibodytiters after immunization against hepatitis B virus (HBV).

Methods Fifty nine healthy infants were vaccinated at birth, 1, and 6 months of age with hepatitis Bvaccine, with follow up to 7 months of age. Infants were randomized into two groups according to needlelength of first vaccine at birth. First group vaccinated with standart needle length and other group receivedvaccine by longer needle length.

Results Macrosomic infants who were immunized with a longer needle achieved significantly higher antibodytiters to hepatitis B surface antigen than standart needle length (median, 3890.2 vs 1311.7 mIU/mL, respectively; p=0.001).

Conclusions Macrosomic neonates benefit from longer needle length with higher levels of antibody titersafter HBV vaccination.