I only found this one while doing some upkeep for my databases.
Out of all of this year's competitive race winners, only THREE received a second, third or fourth Oscar.
Joe Letteri
Stephen Rosenbaum
Sandy Powell
Every single other winner was a first-time Oscar recipient.
It would take me a bit of research to determine if this has ever occurred previously, or if this is the first so few multi-winners occurred (this isn't including sci-tech winners)