I haven't seen many infected mail come through so far. So I am not sure what this header means. I assume it means that Sophos found, and cleaned Troj/VB-EDF'3'rd.
X-IronPort-AV: E=Sophos;i="4.41,333,1241409600";
v="Troj/VB-EDF'3'rd";
d="txt'?exe'96?zip'96,48?scan'96,48,96,217,208,48";a="3033987"
:?