Shorter: it doesn't mean re-running elections or holding by-elections.
1/short thread
Each country has different ways of dealing with the issue - which was foreseen in the current EP elections legislatino that was passed nationally. /2
europarl.europa.eu/factsheets/en/…
This means you can't elect four MEPs and then choose top 3 until UK leaves and IE takes fourth seat...becuase if you ran only a 3-seat election you would get different top 3, than if ran 4-seat /4