Crush strawberries; transfer to a Dutch oven. Stir in pears, lemon juice and pectin. Bring to a full rolling boil over high heat, stirring constantly. Stir in sugar, return to a full rolling boil. Boil for 1 minute, stirring constantly. Remove from heat; skim off foam. Stir in vanilla.
Ladle hot mixture into hot half-pint jars, leaving 1/4-in. headspace. Remove air bubbles and adjust headspace, if necessary, by adding hot mixture. Wipe rims. Center lids on jars; screw on bands until fingertip tight.
Place jars into canner, ensuring that they are completely covered with water. Bring to a boil; process for 10 minutes. Remove jars and cool.