Hooker Lee Barron and scrum-half Ben Murphy have been ruled out of the U20 Six Nations through injury.
Ireland's campaign begins against Scotland in Cardiff on Saturday (2pm, RTÉ1) with Levi Vaughan and Will Reilly called up to the 34 man squad which departs Dublin on Thursday.
Barron and Murphy join hooker Tom Stewart, out-half Cian Whooley and second row Joe McCarthy in being unavailable through injury for the game.
The squad face a hectic schedule of games after Saturday's opener. They go head-to-head with Wales on Friday, 25 June (8pm) and England on Thursday, 1 July (8pm). Ireland's Championship will conclude with ties against Italy on Wednesday, 7th July (2pm) and France on Thursday, 13th July (4.45pm).
Ireland coach Richie Murphy said: "It is always really unfortunate when a player misses out through injury and it is a double blow to lose Lee and Ben so close to our first game, but it's a great opportunity for the two players coming in now. We have prepared really well over a number of five-day camps at the IRFU High Performance Centre and the group is just excited to get over to Cardiff and get stuck into the challenge ahead. We know it'll be tough against Scotland but we're looking forward to getting the Six Nations underway."