The 88-year-old man and 94-year-old woman are being monitored but are showing no signs of an adverse reaction.
They are both residents at the Holy Spirit Nursing Home in Carseldine.
The doctor responsible for the overdoses has resigned.
Health Minister Greg Hunt said the deputy chief medical officer would review the events and file a report.
"Significantly, the patients themselves are showing, at this point, on the latest advice that I have, five minutes before joining us, absolutely no adverse reaction," he told reporters in Canberra on Wednesday.
"The rollout continues. There will be cases. There will be challenges. This has happened in other jurisdictions overseas."