Although differences were not statistically significant , RR participants had a lower incidence of HIV infection by 51 % ( IRR = 0.49 , 95 % CI : 0.16 to 1.48 , P = 0.204 ) and any STI by 37 % ( IRR = 0.63 , 95 % CI : 0.21 to 1.93 , P = 0.418 ) than WP participants .