Adoption was immediate. Propertius announced before publication that something greater than the Iliad was being born, and within a generation the Aeneid was the standard Latin school text, a position it held for as long as Latin was taught in the ancient world. Graffiti at Pompeii quote its opening words. Commentaries accumulated, the fullest surviving being that of Servius in the late fourth century, which remains a major source for Roman religious antiquities because Servius explains cult details his readers no longer knew.
The poem also acquired an oracular function. The sortes Vergilianae was the practice of opening a copy at random and reading the line the finger fell on as a prediction; the Historia Augusta reports several emperors consulting it, and the custom survived into the medieval and early modern periods. The same treatment was given to the Bible and to Homer, and it says something about how a text with no religious authority could acquire religious use.
Christian readers kept Virgil in a way they did not keep most pagan poets, partly because the fourth Eclogue, with its prophecy of a child and a returning golden age, was read as foretelling Christ. He therefore passed intact through the Middle Ages, was credited in some traditions with magical powers, and reached Dante, who made him the guide through Hell and Purgatory and called him master and author. That is an unusual afterlife for an epic written to flatter a Roman emperor.
The manuscript tradition is correspondingly rich. Several late antique copies survive in whole or in part, among them the illustrated Vergilius Vaticanus and Vergilius Romanus of the fourth and fifth centuries, which is more than can be said for almost any other classical Latin author. Continuous copying meant the text never had to be recovered; unlike much of antiquity, Virgil was simply never lost.