Varadkar said the government is currently awaiting advice and that a fourth dose would probably only be for vulnerable groups.
He expects any such vaccine programme to begin before the winter season.
"We're also giving consideration as to whether we need to start on a fourth dose programme, particularly for older people in those who are medically vulnerable," he said.
Varadkar confessed to Europe being in the midst of a second wave of Omicron, but ruled out reimposing restrictions.
Speaking at Sunday's commemoration for victims of the pandemic, Varadkar said that there are over 1,000 people in hospital with COVID, a reminder that the pandemic remains an "ongoing cause for concern, but not a cause for panic."
"It is a very different situation at the moment," he said. "About half of those in hospital with Covid would be in hospital anyway, it's incidental finding in their cases. This is another wave but we don't anticipate it will necessitate the reimposition of restrictions, but other things need to continue. We need to make sure that people have those boosters and third doses."
Varadkar encouraged anyone yet to receive a booster to do so.
