Passing Data Parameters to Oracle Query

"with" SELECT        TRUNC(TO_DATE(: StartDate, 'yyyy-mm-dd')) p_date
              FROM            dual AS parameters
                                           SELECT        vax_feed_dt, create_dt, vax_file_name, vax_feed_type, load_status
                                            FROM            vax_load_audit
                                            WHERE        trunc(vax_feed_dt) between parameters.p_date - 8 and  parameters.p_date

The above is not working fine for me. Can anyone help on this

StartDate is a report parameter Datatype as Date.