Significantly more homeless persons receiving permethrin-impregnated underwear than homeless persons receiving the placebo were free of body lice on day @ in the intent-to-treat population ( @ % vs @ % ; P = @ ) , with a between-group difference of @ percentage points ( @ % CI , @-@ @ ) , and in the per-protocol population ( @ % vs @ % ; P = @ ) , with a between-group difference of @ percentage points ( @ % CI , @-@ @ ) .