Nana's Fluffy Cheesecake

8oz cream cheese, softened
8oz cool whip
1/3 cup sugar
1 cup sour cream
2 tsp vanilla
1 graham cracker crust

Beat cream cheese until smooth.  Gradually add sugar, blend in sour cream and vanilla.  Fold in cool whip and spoon into graham cracker crust.  Chill for 4 hours before serving.