McLaren's Hamilton has struggled for large parts of the ongoing season and currently sits fifth in the drivers' standings.
"I never thought Lewis was gone, so there is no point [in saying] that he is back," Vettel told Sky Sports News.
"He is a very good driver and I respect him a lot for that. The moment he has better results is the moment people will start to be quiet again and hopefully leave him alone."
Hamilton, 26, won the World Championship in 2008 but has yet to regain the title.