Anti-tetanus toxoid antibody IgG geometric mean concentrations were lower in the consistent limb group ( 163 IU/mL [ 95 % CI 140-190 ] ) than in the alternating limb group ( 230 IU/mL [ 197-268 ] ) at 13 months ( p = 00008 ) and at 24 months ( 044 IU/mL [ 037-052 ] vs 061 IU/mL [ 051-073 ] ; p = 00074 ) .