Just a thought before I have a chance to look up the answer to your question. Most Protestants are taught that when the Pope, or Catholic Church makes an infallible declaration, it is a “New Dogma” or new teaching. What an Infallible declaration means to a Catholic is a response to a question regarding an important teaching of the Church that some have called into question.

There are any number of statements that people like Hislop and others have written that misinform the Protestant mind.

Beottener and other have written that the Catholic Church added books to the Bible at Trent. This is a false assertion. Trent responding to the editing of Protestant teachers like Luther, who removed those books from the Old Testament, and called into question some of the New Testament, stated in the strongest of words that the Catholic Church maintained the same books as she had previously defined as part of the Canon.

Prior to the definition of the Dogmas of the Immaculate Conception and the Assumption, there was a long history of the celebration of the two feasts in both the Eastern and Western Church. While they were not on the calendars of all the diocese of the world, they were in most. Missals and prayers going back to the early 300’s include both feasts. When the question came up, and some people started to deny that these were authentic Catholic teachings it became important to settle the issue, once and for all. So it was studied, and when the Popes (Pope Piux IX and Pope Pius XII in these two cases) had gathered the information, prayed and felt it was opportune, they made the formal and Infallible declarations, which made the teachings not just an ancient and venerable teaching, but a Dogma, or teaching that one had to recognize in order to be a faithful Catholic.

An example of a teaching that is not Dogma would be Limbo. Limbo is considered a pious belief, it is Theological speculation about what happens to the souls of infants and young children who die without being baptized. One theory is that they go to a place of perfect natural happiness, (as opposed to heaven which is a place of perfect SUPERnatural happiness.) Others believe that God will grant the soul of the unbaptized who had no chance to hear the Gospel or were not baptized through no fault of their own full knowledge of His nature, and they can choose or reject Him. If they choose Him they enter heaven. As the Church has not defined this as Dogma, Catholics are free to accept or reject either notion, and still be considered Catholics in good standing.

So Infallible declarations really don’t “invent” new teachings, but clarify those teachings that have been attacked or come into question. They don’t change what the Church teaches, but rather clarify what has always been taught.