Frenchman Prost won his championships with two teams over nine years but Vettel is aiming for four in a row, a feat achieved before only by Argentine great Juan Manuel Fangio and Michael Schumacher.
Only three drivers have ever won four or more titles since the championship started in 1950.
"Oh yes, although I hope he doesn't have a start to the season like he did two years ago when he won four or five races in a row," the 58-year-old told reporters at a Renault engine event on the outskirts of Paris when asked whether Vettel would chalk up his fourth crown.
Vettel won five of the first six races in 2011 when he romped to his second title but he had a much tougher time last year, being taken down to the wire in Brazil by Ferrari's Fernando Alonso.
"He is still the favourite. Behind him, it's hard to say," said Prost who won his titles with McLaren and Williams.
"Will losing (Lewis) Hamilton and having a young driver in his place be destabilising (for McLaren)? Mercedes will not be challenging for the title, I don't think so. Alonso could be the most dangerous behind Vettel and why not an outsider like (Lotus's Kimi) Raikkonen or (Romain) Grosjean?"
Prost's son Nicolas is a development driver with Lotus.
Asked what conclusions he had drawn from the first two pre-season tests in Spain, Prost said Red Bull were still clearly the team to beat while Hamilton's Mercedes team would be fighting to catch the other front-runners.
"Red Bull are still there and certainly better than last year at the same time," he said. "Ferrari are also good. McLaren will be certainly among the top three and Lotus also up there.
"There's a little question mark over Mercedes, we still don't know their level. They were a long way away at the end of last season so I don't see them suddenly returning to the front. But they will be up there at certain tracks.
"It could be a very even field, we'll see some good races."
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