Lauda was taken ill while on holiday in Spain and doctors estimated he had just days to live when he was hospitalised in his native Austria.
Well-wishes were expressed up and down the F1 paddock and across the wider motorsport world.
But Lauda has revealed that the time taken by Vettel set his correspondence apart.
Lauda told La Gazzetta dello Sport: “One of the things that pleased me most is a letter sent by Sebastian Vettel, written in his own hand, full of nice words and affectionate considerations.
“I did not expect it, Usually the drivers do not do these things, they just drive, but he is a beautiful person.”
Vettel fell short of Lewis Hamilton in the drivers’ championship for a second year on the bounce in 2018, but Lauda has no doubt that the Ferrari man will return with a renewed challenge next season.
“Yes, he has had difficult moments of discomfort, we know, but it would be absurd to question him.
“He will recover, a champion never forgets how he drives. He will be the great rival of Hamilton in 2019.”
Source: GP Fans