In a medium saucepan, combine water, sugar, frozen raspberries, and vanilla bean. Bring to a boil, then reduce heat and simmer for 25 minutes, stirring occasionally. Syrup will darken in color and thicken slightly.

Pour the mixture through a fine mesh sieve, pressing lightly on the solids with a rubber spatula. Discard the solids and place the syrup in the refrigerator until chilled.

Pour desired amount of syrup into a glass and top with club soda. I like a 1:3 syrup to club soda ratio. If desired, add a splash of half and half. Serve immediately.