In winning the Japanese GP for a fourth time in five seasons, Vettel also set a personal best record of five consecutive victories after triumphing in Belgium, Italy, Singapore and Korea.
The 26-year-old German will, however, have to wait another fortnight for the race in India before taking the title as Alonso finished a distant fourth in his Ferrari, 45 seconds adrift.
It means Vettel now has a 90-point cushion over Alonso with only 100 up for grabs, leaving the Spaniard facing the inevitable.
Asked whether the title fight was still on, Alonso replied: “I don’t think so. Even if Sebastian retired from all four remaining races, I would have to win all of them, so it’s only a matter of time before he will be champion. We have different goals now.
“We will continue to try to do out best on Sundays, and when it is mathematically settled we will congratulate him.”
Starting from eighth on the grid, it was apparent from the off Alonso would be unable to challenge Vettel, Red Bull teammate Mark Webber and Lotus' Romain Grosjean, who completed the podium.
“We weren’t as quick as the Red Bulls or Grosjean, so fourth was the maximum we could achieve,” added Alonso.