The young people of the Casa San Lorenzo youth association in Rome, founded by Blessed Pope John Paul II, are among the faithful in St Peter’s Square.
Vatican Radio spoke to the director of the centre, Katya Tootill, to find out why it is so important for young people to take part in the vigil.
"It is important because the general political atmosphere in the world, everything that is going on also has to do something with us youth, it's also our concern... This "Pope's call for peace, to fast, to pray for peace is important..."
She adds that with regard to the centre's contribution to the vigil is important because, "youth are the future of the world, of the Church and therefore this is what we can bring."