Vermaelen does not believe the speculation or reception from the Gunners' supporters in Germany have had a negative effect on the striker, who scored 37 goals last season.
"To me he looks fit and sharp in training," said Vermaelen.
"He's working hard. He's working on his fitness. I don't see anything (different) and I hope he stays the next four years as well.
"I don't know what happens behind the scenes but at the moment I can only say he's a player for Arsenal.
"I feel really positive for the new season. If we all stay fit, the squad is strong enough to compete for the title."