In a saucepan, combine the blueberries, sugar, and water.

Bring the mixture to a boil over medium heat, stirring occasionally.

Once boiling, reduce the heat and let it simmer for about 10 minutes, or until the blueberries burst and the mixture thickens.

Remove from heat and stir in the lemon juice and vanilla extract, if using.

Let the syrup cool slightly before transferring it to a jar or container.