Victoria 2 Wiki
This article is considered accurate for the current version of the game.
The Vega Expedition is a decision unique to Sweden. It can also be taken by Scandinavia with Swedish as primary culture.
It shows up in the tab when the decision Build the Suez Canal has been taken. It does not require, that Sweden takes it, just that any great power takes it.
It can be taken when Sweden has researched iron steamers and Biologism.
It gives 5 prestige and 0.05 years worth of research points. It also removes 1 Infamy.