On January 24, 2005 the Prefect of the Vatican Congregation for Clergy, Cardinal Darío Castrillón Hoyos, in a letter issued by the Ministry and addressed to Priests on the occasion of the Year of the Eucharist, reminds them about their duty to «guard especially children as the first receivers» of the Eucharist.
Here is the original text:

 

Vatican City State, 8 January 2005

Dear brother priests,

By means of this e-mail, I wish to address those of you who are connected with our website, www.clerus.org, which offers information for permanent/ongoing formation, thanks primarily to the international theological video-conferences organized by the Congregation for the Clergy, which have taken place for more than three years on specific themes of interest.  (...)
The Holy Father stressed the importance of children to the Church in his Angelus Address of January 6th, the Solemnity of the Epiphany:  "Children are the present and future of the Church. They play an active role in the evangelization of the world and, with their prayers, help to save and improve it.”
In this year of the Eucharist, how can we not think in a special way about the first recipients of the catechetical message in our parishes:  the children.  We receive them first at the baptismal font accompanied by their family, and then we see them present in our parish, more frequently than before, as they participate in the course of catechism in preparation for First Holy Communion! 
Pope Saint Pius X, a great Pope canonized by the Church, dedicated no small attention and pastoral effort to children.  On August 8, 1910 he issued the Decree “Quam Singulari,” in which he established that children could receive First Holy Communion at the age of seven. 
Important to the pastoral care of children is allowing them to approach the eucharistic Communion, after they have received the necessary preparation in their parishes to learn the primary and fundamental elements of the Christian faith, without their having to wait unduly long.  The age of discretion comes individually, around seven years, when common bread can be distinguished from the eucharistic bread, the true Body of Christ. 
Few are unconvinced, together with Pope Saint Pius X, that the praxis of allowing children First Holy Communion at the age of seven has brought great graces to the Church.  The rest must not fail to remember that in the early Church, the Sacrament of the Eucharist was administered to babies immediately after baptism, under the species of a few drops of wine. 
To allow children to receive the Eucharistic Jesus as soon as possible has been for many centuries one of the strong points of the pastoral outreach to the smallest members of the Church.  The custom reestablished by Pope Saint Pius X in his time has been praised by his Successors, including our own Holy Father John Paul II.  Canon 914 completely sets forth the Papal thought:  "It is primarily the duty of parents and of those who take their place, as it is the duty of the parish priest, to ensure that children who have reached the use of reason are properly prepared and, having made their sacramental confession, are nourished by this divine food as soon as possible.
The Holy Father has recently recalled the decision of Pope Saint Pius X in his recent book "Rise, Let Us Be On Our Way”:  "My predecessor Saint Pius X gave a touching testimony to his pastoral love for children by the changes he introduced regarding the reception of First Holy Communion.  Not only did he lower the age for approaching the Eucharistic Table (I was able to take advantage of this in May, 1929), but he also introduced the possibility of receiving Communion before the age of seven, if the child demonstrates sufficient understanding.  This pastoral decision to bring forward the reception of Holy Communion is most commendable.  It as yielded rich fruits if holiness in children and in the apostolate among the young, in addition to a flowering of priestly vocations." (John Paul II, "Rise, Let Us Be On Our Way,” Rome 2004, p. 103).  
We priests, called by God to the custody of the Most Holy Sacrament of the Altar in union with our Bishops, can and must see children above all as the first recipients of the immense gift of the Eucharist, which God has placed in our fragile jars of clay, our consecrated hands. 
I believe that one of the greatest joys of a parish priest is to hear the First Confession of children and, afterwards, to give them First Holy Communion.  It come spontaneously to my mind that the younger such children are, then greater is the likelihood of their more heartfelt and worthy welcoming of Christ in the Sacrament.  In fact, the mind of the child, reaching the age in which it begins to reason - and today this age is reached early - is open and available to the acceptance of the divine light, that penetrates as far as possible the mystery of the love of God for man.  Faith can raise us over reason, and this faith – as we have often experienced it in our parishes - is very much alive in the children that are able to express with prayer their closeness to the Lord sometimes better than ourselves
Therefore, we hope that the holy custom, of which we are reminded by all of the recent Popes, by which the Most Holy Eucharist is given to small children after they have made their First Confession, is more appreciated and assiduously implemented, particularly in this Year of the Eucharist.  Let us unite ourselves in prayer so that “pastoral charity” will be the motivating force behind Parish Priests who are devoted to parish work, in union with their Bishops, and with families and educators of children, so that love for the Blessed Eucharist will be passed on to children of even the most tender years and that the desire to receive the Body of Christ will become the surest way to assure a future of peace and holiness, not only for individual members of the faithful but for the whole Christian community.

United in prayer and in pastoral zeal, I remain most devotedly in Christ,

Darío Card. Castrillón Hoyos

Prefect of the Congregation for Clergy