The Gunners are two points clear at the top of the Premier League despite slipping to their second loss of the season at Old Trafford, after winning eight games in a nine-match unbeaten run.
Vermaelen has conceded that failing to take points off United represents a "missed opportunity" for the league leaders, but believes that the Gunners should trust their own ability to regain top form after the international break.
He told the club's official website: "We wanted to win the game and went to Old Trafford to do that. We were eight points ahead of United going into the match and had the chance to make it 11 points.
"It was a bit of a missed opportunity. But we're still top of the league and need to keep the confidence we've had over the last couple of weeks.
"There's no reason for that to change dramatically. We're still confident we can win games and we have a long way to go."
The Belgian international has also moved to quieten speculation over his future at the Emirates, insisting that he remains committed to life in North London following his first league start of the season on Sunday.