Reasons for omitting the Creed when it would normally happen:
The Creed is optional when there are the Scrutinies, (prayers for the elect who are to be baptised a few weeks later.) From the book Rite of Christian Initiation of Adults: “… then, if required, the profession of faith is said. But for pastoral reasons these general intercessions and the profession of faith may be omitted.” (RCIA, n. 143, 157, 164 edition for Australia and England, n. 156, 170, 177 in the edition for the USA.).
The usual time for the Scrutinies is the Third, Fourth and Fifth Sundays of Lent. However, from the RCIA book with the Australian number “133. … When, because of unusual circumstances and pastoral needs, the period of purification and enlightenment takes place outside Lent, the scrutinies are celebrated on Sundays or even on weekdays, with the usual intervals between celebrations. They are not celebrated on solemnities of the liturgical year” (USA RCIA, n. 146).
At the Easter Vigil there is a renewal of baptismal promises, instead of the Creed.
For Easter Sunday, the 2010 Roman Missal has: “In Australia, England and Wales, and in Scotland: The Creed is said. However, in Easter Sunday Masses which are celebrated with a congregation, the rite of the renewal of baptismal promises may take place after the homily, according to the text used at the Easter Vigil (p. 418). In that case the Creed is omitted.”
If there is a baptism at Mass, from the Rite of Baptism for Children “29. … 2 … c. The Creed is not said, since the profession of faith by the entire community before baptism takes its place.” (The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 374).
And if there is a confirmation at Mass, from the Rite of Confirmation “31. … a) the profession of faith is omitted, since it has already been made;” (The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 492).
If there is an ordination of a deacon, priest or bishop in the Mass, from the rite of “Ordination of Deacons, Priests and Bishops”, n. “The profession of faith is not said, nor are the general intecessions.” (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, pages 28, 39, 66).
If there is a consecration to a life of virginity in the Mass: “12. … b) the profession of faith is not said, even if prescribed by the rubrics of the day”. (The Rites Volume Two, Liturgical Press, 1991, ISBN: 0-8146-6037-1, page 161, 177).