Vacca was a sixth century grammarian who studied and commented on the works of Lucan

Marcus Annaeus Lucanus

Marcus Annaeus Lucanus , better known in English as Lucan, was a Roman poet, born in Corduba , in the Hispania Baetica. Despite his short life, he is regarded as one of the outstanding figures of the Imperial Latin period...

. Little is known of Vacca other than he wrote Vita Lucani (Life of Lucan), which is not to be confused with Suetonius

Suetonius

Gaius Suetonius Tranquillus, commonly known as Suetonius , was a Roman historian belonging to the equestrian order in the early Imperial era....

' Vita Lucani.

Vacca's commentaries were used in medieval study of Lucan. Though he is not named, evidence of Vacca's writing appears in the tenth century works Commenta Bernensia

Commenta Bernensia

The Commenta Bernensia, also known as the Bern scholia, are commentaries or marginal notes in a 10th-century manuscript preserved in the Burgerbibliothek of Bern, Switzerland....

and Adnotationes super Lucanum.

Vacca's Life of Lucan gives sole accounts of many of Lucan's lost works as well as accounts of the feud between Lucan and Nero

Nero

Nero , was Roman Emperor from 54 to 68, and the last in the Julio-Claudian dynasty. Nero was adopted by his great-uncle Claudius to become his heir and successor, and succeeded to the throne in 54 following Claudius' death....

, which agrees with Tacitus

Tacitus

Publius Cornelius Tacitus was a senator and a historian of the Roman Empire. The surviving portions of his two major works—the Annals and the Histories—examine the reigns of the Roman Emperors Tiberius, Claudius, Nero and those who reigned in the Year of the Four Emperors...

' and contradicts Suetonius

Suetonius

Gaius Suetonius Tranquillus, commonly known as Suetonius , was a Roman historian belonging to the equestrian order in the early Imperial era....

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