Sprinkle the gelatin over 1/4 cup boiling water. Let stand, stirring occasionally, until dissolved, about 5 minutes.
Using an electric mixer, beat cream cheese until smooth.
Mix in the pumpkin, sour cream, sugar, pumpkin pie spice, and vanilla.
Mix in the gelatin mixture until incorporated.
Pour the mixture into the crust and refrigerate, covered, until firm, at least 2 hours and up to 2 days.