Diadexus (VXGN) 10-Q 2005 Q1 Quarterly report

Exhibit 32.1

SECTION 1350 CERTIFICATION

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C.ss.1350, as adopted), James P. Panek, Chief Executive Officer of VaxGen, Inc. (the “Company”), and Matthew J. Pfeffer, Chief Financial Officer of the Company, each hereby certify that, to the best of their knowledge:

1. The Company’s Quarterly Report on Form 10-Q for the period ended March 31, 2005, to which this Certification is attached as Exhibit 32.1 (the “Report”) fully complies with the requirements of section 13(a) or section 15(d) of the Securities Exchange Act of 1934, and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

In Witness Whereof, the undersigned have set their hands hereto as of the 30th day of May, 2007.

/s/ James P. Panek   /s/ Matthew J. Pfeffer

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Chief Executive Officer Chief Financial Officer

This certification accompanies the Form 10-Q to which it relates, is not deemed filed with the Securities and Exchange Commission and is not to be incorporated by reference into any filing of VaxGen, Inc. under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended (whether made before or after the date of the Form 10-Q), irrespective of any general incorporation language contained in such filing.

End of Filing

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