In a 3-quart pitcher, combine the lemonade concentrate, water, sugar and salt. Stir until sugar is dissolved.
If you are using vanilla beans, split the beans lengthwise down the middle and scrape out the seeds into the lemonade mixture.
Discard the beans. Stir until the seeds have separated.
Alternately, add vanilla extract to taste.
Let the lemonade steep for at least 10 minutes.