Combine the first 4 ingredients in a medium saucepan. Scrape seeds from vanilla bean; add seeds and bean to wine mixture. Bring to a boil; reduce heat, and simmer 5 minutes. Strain mixture through a sieve over a large bowl; discard solids. Let cool 30 minutes; discard rind. Stir in strawberries and oranges. Cover and chill. Garnish with mint sprigs, if desired.