Table 2.  Independent factors associated with core antibody breakthrough infection Variable No (%) of breakthrough infections Adjusted odds ratio (95% CI) P value for variable Vaccination group (median time (years) since vaccination):   Group 1 (13.6)  21/52 (40) 8.9 (3.8 to 20.8) 0.0001   Group 2 (13.6)  18/56 (32) 9.0 (3.8 to 21.1)   Group 3 (13.6)  14/63 (22) 7.7 (3.2 to 18.5)   Group 4 (10.7) 25/220 (11) 3.3 (1.6 to 7.1)   Group 5 (6.3)  9/202 (4) 1.3 (0.5 to 3.3)   Group 6 (2.1) 15/254 (6) 1.0 Sex:   Male 60/426 (14) 1.6 (1.0 to 2.6) 0.04   Female 42/421 (10) 1.0 Peak antibody (mIU/ml):   <10  19/39 (49) 11.9 (4.9 to 28.8) 0.0001   10-99  12/58 (21) 3.4 (1.5 to 7.8)   100-999 36/224 (16) 1.8 (1.0 to 3.2)   1000 33/449 (7) 1.0 Village:   Manduar 34/223 (15) 1.8 (1.1 to 3.0) 0.03   Keneba 68/624 (11) 1.0