He replaces Shaun Knight (Gloucester Rugby), who has returned to Kingsholm to have his sore left knee assessed by the club’s medical team.
Swainston, 23, has made 13 first team appearances for Wasps after joining the club from Leeds Carnegie last summer.
His call-up comes after a string of impressive performances for the Club in recent months. Swainston has previously represented England at U18 and U20 level and he will join Wasps team-mates Christian Wade, Elliot Daly and Joe Simpson in the current Saxons squad.