Any individual described under subsection (a) of this section who is employed by the Center on or after August 14, 1991, shall be deemed an employee under section
8901
(1) of title
5 for purposes of health insurance coverage under chapter 89 of such title. An individual described under subsection (a) of this section who is an employee of the Center on August 14, 1991, may elect coverage under this subsection during the 31-day period beginning on August 14, 1991, and during such periods as determined by the Office of Personnel Management for employees of the Center employed after August 14, 1991.