"I am a realist. I am not naive. I will reserve my final judgment for doping in these Games for February 2018," IOC chief Jacques Rogge said.
The IOC is freezing all 2,100 samples it has collected during the February 12-28 Games for an eight-year period to allow re-testing for substances that may not be traceable or known now but could surface in the future.
Tests may also not exist yet but could be developed in the coming months or years.
Extensive pre-Games drugs testing by federations and national doping agencies months before the Olympics nabbed about 30 offenders and may have scared off others.
Days before the February 12 opening ceremony it looked like these Games would follow the pattern of past Olympics when Terenteva tested positive for a mild stimulant.
She got off with a reprimand and ended up being the only positive test.
But as was the case at the Beijing Olympics in 2008 where re-testing of samples months later revealed six more positive tests, the IOC will not close the book on Vancouver until after the eight-year period.
"Surely, we are having cleaner and cleaner Games," IOC medical commission chief Arne Ljungqvist told Reuters.
"The pattern seems to be fairly clear... people are being caught more before they become Olympians and we find less and less (doping) during the Games.
"They (testers) are identifying drug takers at an earlier stage. The cheats are out before they arrive."
Ljungqvist conceded some blood samples from Vancouver would need to be retested for what might be a new generation of blood-boosting EPO.
The coming months will provide a clearer picture whether the Vancouver Olympics marked the start for clean Games or a new chapter in doping with substances that at the time could not be detected.