Table 1.  Vaccine efficacy in 1998 against chronic carriage of hepatitis B virus and breakthrough infection overall by village and by age group Chronic carriage Breakthrough infection No infected in vaccine v control Vaccine efficacy (%) (95% CI) No infected in vaccine v control Vaccine efficacy (%) (95% CI) Overall 10/855 v 191/931 94 (89 to 97) 102/847 v 564/929 80 (76 to 84) Keneba 6/628 v 83/622 93 (84 to 97) 68/624 v 302/620 78 (72 to 82) Manduar  4/227 v 108/309 95 (87 to 98) 34/223 v 246/309 81 (74 to 86) <5 years (group 6) 3/235 v 68/354 93 (79 to 98) 14/232 v 140/354 85 (74 to 91) 5-9 years (group 5) 0/225 v 66/309 100 10/224 v 309/509 93 (85 to 96) 10-14 years (group 4) 2/220 v 39/191 96 (82 to 99) 33/220 v 156/190 82 (75 to 87)  15 years (groups 1, 2, 3) 5/175 v 18/77 88 (68 to 95) 53/171 v 68/76 65 (56 to 73)