Professor Luke O'Neill says scientists are expecting that COVID-19 case numbers will start falling later this month as Omicron "runs out of road".
The Trinity College immunologist also says the evidence is growing stronger every day that the variant causes less severe disease than previous strains.
COVID-19 numbers remain at record high levels in Ireland, with around 20,000 cases being reported daily for over a week now.
There's also concern that many cases aren't being detected in the community, with testing positivity still above 50% some days.
Professor O'Neill told The Pat Kenny Show that some estimates suggest as much as 40% of the world's population will be infected with the new strain.
He observed: “The hope is it will protect against reinfection and stop severe disease.
"Eventually, there will be no point in counting cases, because it’s so widespread - the number of cases isn’t so informative in that situation.”
While transmission continues at a high level, Professor O'Neill says evidence has also "grown and grown" that Omicron is causing milder illness in individuals than previous strains.
He observed: “All over the world, everybody is reporting the same thing - you get infected and it’s a mild disease, and you don’t end up in the ICU.
“We’re now 11 days since Christmas when there would have been loads of mingling. We aren’t seeing a huge increase in the ICU yet, which would have happened with Delta.
“Let’s hope in the next few days that continues. Within a week or two it will be even clearer.
“We’re all predicting towards the end of January it will start to go down. The virus runs out of road: it has infected everyone, basically, and there’s no one left to infect. Therefore the case numbers go down.”
One feature of Omicron is that many people who've had COVID-19 already are now getting reinfected.
However, Professor O'Neill says that's less of a concern if your immune system is protecting you from severe illness.
He said: “Remember, [the virus] stays in your nose… you might have a few sniffles, but it won’t progress into breathing difficulties because your lungs are protected.
“Of course, the boosters are tremendously protecting your lungs. People seem to forget that the main effect of vaccines is to protect your lungs and prevent severe disease.”
Professor O'Neill said the dream is that Omicron is “the last game in town” when it comes to COVID-19 - a variant that eventually becomes endemic across society.
However, the remaining concern is that another variant could also emerge that causes more serious illness than Omicron.
The Trinity immunologist says that shows the need to get vaccines to developing countries “as quick as we can” to reduce the chance of any such new 'variant of concern' cropping up.