England have five matches approaching in the second stage of the tournament and all against Test opposition. They next play 1996 champions Sri Lanka in Antigua on Wednesday.
"Very rarely do you play a 100 percent game and at the minute we're playing at about 80 percent," Vaughan told reporters after the 48-run win over the Irish. "I'd like to see us playing a bit more than that."
England were 113-4 at one stage against Ireland before Paul Collingwood helped them reach 266-7. Then with the ball, England lacked penetration as some Irish batsmen occupied the crease for long periods.
Although Vaughan knows his side have more improvements to make, he was relieved to get points on the board.
They lost to New Zealand in Group C so took no points through to the next stage.
"We just needed to win the match and take the two points," he said. "There are obviously areas where we need to improve but there are also areas where we were very good as well.
'NAIL HOME'
"It would have been nice to nail home the Irish when we had them six down and when we had got the rate to 11 an over, but that wasn't to be and they played well and we just didn't quite get it right for a few overs.
"In the last five overs we showed that we can get it right. We need to try and bowl teams out when we get an opportunity, when they're five or six down, as we haven't done that yet."
Vaughan, who described the Ireland game as a potential "banana skin" said if he had the chance again he would have bowled first, after the cracks in the pitch that concerned him failed to have any impact on the match.
England have reached three World Cup finals but are yet to win the event.
