 Sione joined Saracens at the beginning of January 2018 to act both as injury and international call-up cover, with an initial contract to the end of the 2018/19 season.Several injuries, including to his hand, would limit him to four games across all Saracens' competitions in the remainder of the 2017/18 season.In February 2019, Sione announced his signing by Wasps, in order to receive more game time and to partially fill the position vacated by Nathan Hughes who departed at the conclusion of the 2018/19 season.