It’s even older than the Vulgate. In his Lives of Famous Men, which he wrote by the end of the 4th century, St. Jerome (the saint who was responsible for the revision of the Gospels and the translation of the Hebrew Scriptures into Latin), mentions the Bishop of Aquileia, Fortunatianus. Jerome explains that the cleric had written a commentary on the Gospels, which the saint described as “a pearl without price.” In fact, when writing his commentary on the Gospel of Matthew, Jerome used Fortunatianus’, the earliest Latin commentary on the Gospels registered in history.
This commentary was lost for more than 1,500 years. Until now.
Even though there are plenty of references to Fortunatianus’ text in other ancient works, as Hugh Houghton explains in this post published by The Conversation, “no copy was known to survive until Dr Lukas Dorfbauer, a researcher from the University of Salzburg, identified Fortunatianus’ text in an anonymous manuscript copied around the year 800 and held in Cologne Cathedral Library.” The manuscript found in the Cathedral indeed preserves the original form of Fortunatianus’ commentary on the Gospels.
You can read the whole article, by Hugh Houghton, here. And you can read Fortunatianus’ work, in English, here.