The varenicline group had significantly higher continuous abstinence rates vs the placebo group during weeks 21 through 24 ( 37.8 % for the varenicline group vs 12.5 % for the placebo group ; RD , 25.2 % [ 95 % CI , 21.1 % -29.4 % ] ; RR , 3.0 [ 95 % CI , 2.4-3 .7 ] ) and weeks 21 through 52 ( 27.0 % for the varenicline group vs 9.9 % for the placebo group ; RD , 17.1 % [ 95 % CI , 13.3 % -20.9 % ] ; RR , 2.7 [ 95 % CI , 2.1-3 .5 ] ) .