It is believed the baby was born in Switzerland, but even its name is not publicly known.
Told during an interview with Germany's Welt am Sonntag that he obviously does not like to talk about his new family, Vettel insisted: "And even now I will not.
"Private is private."
When the 26-year-old named his 2014 Red Bull car 'Suzie' in Melbourne on Tuesday, many thought it might be a hint as to his daughter's name.
But Bild newspaper said: "Not so."
Given Vettel's notoriously guarded nature, it is little surprise the sports research firm Repucom this week found that fiery Fernando Alonso, flamboyant Lewis Hamilton and even likeable Felipe Massa are all more commercially marketable than the highly-successful Vettel.