On May 23, 2019, we implemented a strategic organizational restructuring, principally to align our operations around our vaccine business and significantly curtail further investment in our immuno-oncology business. In connection with the restructuring, we reduced our workforce by approximately 80 positions, or approximately 36%, of U.S.-based personnel. Also, in connection with the restructuring, our Chief Executive Officer, also a member of the Board of Directors (the “Board”), submitted notice of his retirement from the Company and the Board, effective August 1, 2019. As of December 31, 2020, we have completed our restructuring activities and all costs have been incurred.

The major components of our restructuring costs are summarized as follows (in thousands):

Components of Restructuring Costs	Restructuring Costs Incurred for the Year Ended December 31, 2019
Severance and other termination benefits	$	6,277
Stock-based compensation expense (a)		4,122
Accelerated depreciation		2,957
Total restructuring cost	$	13,356

The outstanding restructuring liabilities are included in accrued liabilities on the consolidated balance sheets. As of December 31, 2020 and 2019, the components of the restructuring liabilities were as follows (in thousands):

	Severance and Other Termination Benefits
Balance at December 31, 2018	$	-
Severance and other termination benefits		6,277
Cash payments or settlements		(5,602	)
Balance at December 31, 2019	$	675
Cash payments or settlements		(675	)
Balance at December 31, 2020	$	-