If you need to get the current_week that is 15 days before today's date then you can use this statement:

Select current_week from #mytable

where GETDATE()-15 between cast(Left(Ltrim(current_week), 10)as date) and cast(right(Rtrim(current_week), 10)as date)

To get a result back from your sample I have used (2012-01-29) 813 days before today's date. The date falls between the begin and end date of your current_week range

Select current_week from #mytable

where GETDATE()-813 between cast(Left(Ltrim(current_week), 10)as date) and cast(right(Rtrim(current_week), 10)as date)

current_week

2012-01-27 ~~ 2012-02-02