CANBERRA, Feb. 24 (Xinhua) -- Two elderly Australians have been given a higher than recommended dose of Pfizer's COVID-19 vaccine, Australian Health Minister Greg Hunt confirmed on Wednesday.

Hunt said the 88-year-old man and 94-year-old woman in Queensland were being monitored but have not shown signs of adverse reaction to the doses.

It has been reported that they both received four times the recommended dose of the vaccine but Hunt could not confirm, saying an investigation was underway.

"It hasn't been confirmed, because it's actually really hard to be able to tell what was in the needle," he told a press conference in Canberra.

The doctor who administered the vaccines has been stood down from the rollout.

"In relation to the individual doctor, we'll leave that to the investigation as to whether or not they either did not understand or did not complete it, but it was a serious breach in terms of following the protocol," Hunt said.

"Both patients are being monitored and both patients are showing no signs at all of an adverse reaction. But it is a reminder of the importance of the safeguards."

It occurred on only the second day of Australia's coronavirus vaccine rollout.

Chief Medical Officer Paul Kelly said that training modules for administering vaccines may need to be reviewed.

"This was a mistake, whether it was simple or not we leave that to the investigation."