This excerpt taken from the PFE DEF 14A filed Mar 15, 2007.
Election of Directors
A plurality of the votes cast is required for the election of Directors. This means that the Director nominee with the most votes for a particular slot is elected for that slot. You may vote for or withheld with respect to the election of directors. Only votes for or withheld are counted in determining whether a plurality has been cast in favor of a Director. Abstentions are not counted for purposes of the election of Directors.