5 HP/MP per Vit/Int up to 20, 6 per stat up to 60, 7 per stat thereafter.
Base stats gained prior to those levels never change in how much they give you. In other words, the base Vit gained from levels 1-19 will always give 5 HP, no matter what level you are; Vit from equipment will always give you the appropriate amount of HP for your level.
There's some formulas on the wiki that adjust for this behavior for Eir/Sieg/Dainn, dunno if there are numbers for the other classes there yet. Too lazy to dig them up, but they're there if you're interested.
"It is not a disgrace to fail. Failing is one of the greatest arts in the world," however --
"Believe and act as if it is impossible to fail." ~ Charles Kettering