Upgrade to Vertex 3.1.0 - Wages Over $200,000

We are testing Vertex 3.1.0 with the two JDE ESUs (JL19407 and JL20260).  JDE doc # 1498255 describes a new change for employees with wages over $200k will be taxed an additional .9% on Medicare, bringing the rate from 1.45% to 2.35%.  I have tested by giving employees a flat $250,000 payment thru interims, and the medicare rate remained at 1.45%.  I did not see any special instructions, or information to activate this functionality other then applying Vertex 3.1.0 and the associated ESUs.  How and when does this rate become effective?