In a video posted online at 3:40 p.m., Ontario Provincial Police Sgt. Kerry Schmidt said the vehicle rollover happened in the eastbound lanes near Brock Road.
Images from the scene showed a severely damaged black car in the ditch between the eastbound and westbound lanes.
The driver was taken by air ambulance to a Toronto trauma centre.
Schmidt said the eastbound lanes of the highway were closed at Brock Road and detours were put in place.
He said drivers were forced off the highway.
The westbound lanes were temporarily closed to allow for the air ambulance to land, Schmidt added.
“I do expect there to be delays and closures on the 407 eastbound at Brock Road for several hours,” Schmidt said at the time.
In an update posted to an OPP Twitter account just after 6 p.m., police said the highway had fully reopened.
“Injures do not appear as serious as first (thought),” the tweet read.
Schmidt told Global News the victim’s injuries were initially believed to be life-threatening, but said that’s no longer the case.