Dr. Shenk intends to "commercialize discoveries made in his Princeton University laboratory in the area of antiviral therapeutics," according to published reports -- and since these would likely compete with Merck's vaccine businesses, he has rightly decided to step down. Thus, from last year's Merck proxy statement:
. . . .Thomas E. Shenk, Ph.D., Age — 65, Elkins Professor, Department of Molecular Biology, Princeton University since 1984. Dr. Shenk was also the Chairman from 1996 to 2004.
Director, Fox Chase Cancer Center since December 2009; Fellow, American Academy of Arts and Sciences; Member, American Academy of Microbiology and National Academy of Sciences and its Institute of Medicine. Dr. Shenk was also a director of Cell Genesys, Inc. from 2001 to 2009 (biotechnology company), CV Therapeutics, Inc. from 2004 to 2009 (biotechnology company) and Merck Sharp & Dohme Corp. (formerly known as Merck & Co., Inc.) from 2001 to November 2009. . . .
So it goes.