From NBC's official press release:

Liz Lemon (Tina Fey) fights for the staff's right to flu shots while Jack Donaghy (Alec Baldwin) looks for creative ways to spend time with Elisa (guest star Salma Hayek).

Chris Parnell guest stars.

Liz (Fey) tries desperately not to catch the flu, but its spreading amongst the TGS cast and crew quickly; and Jack (Baldwin) is being selective over who receives vaccinations from Dr. Spaceman (guest star Chris Parnell).  One is offered to Liz, but she refuses to take it, championing for the rights of the crew.  Meanwhile, Elisa (guest star Hayek) is working seven days a week, so Jack must be creative about finding ways to spend time with her.

30 Rock also stars Tracy Morgan, Jane Krakowski, Jack McBrayer, Katrina Bowden and Scott Adsit.


Source: NBC
(Image courtesy of NBC)