If the ECB keeps the spread down, it is because of the "Draghi Effect" as it hasn't bought any bonds since 2011. That's why the criticism of plans for Quantitative Easing along the lines of "yields are low already, what's the point of QE?" is right (I think it may have been Weidmann to say so).

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman