Jean-Francois Delfraissy told BFM television the "true enemy" for now was still delta, spreading in a fifth wave.
"We should see a progressive rise of the omicron variant, which will take over from delta", possibly by the end of January, he said.
"Christmas is not at risk if the population and decision-makers are all very cautious," he said, reiterating that social distancing and a third, booster shot of vaccines were key weapons in the fight against COVID-19.
France recorded nearly 50,000 new conformed COVID-19 cases over 24 hours, the Health Ministry said on Wednesday.
There were 1,886 people in intensive care units with COVID-19 on Wednesday, a level Delfraissy said was not yet a peak, particularly when compared to 6,000-7000 at the height of the second wave in France last autumn.
The local health body for the Ile de France region of greater Paris said in a statement on Thursday that a case of omicron variant had been found in a person who returned from Nigeria, the first confirmed case in Metropolitan France.