The varenicline group ( n = 760 ) had significantly higher continuous abstinence rates during weeks 15 through 24 vs the placebo group ( n = 750 ) ( 32.1 % for the varenicline group vs 6.9 % for the placebo group ; risk difference ( RD ) , 25.2 % [ 95 % CI , 21.4 % -29.0 % ] ; relative risk ( RR ) , 4.6 [ 95 % CI , 3.5-6 .1 ] ) .