Good Morning Britain's Dr Hilary Jones says everybody will probably get Omicron.
The doctor made the comment on Wednesday during a discussion on the ITV show about cutting self-isolation to five days.
Host Susanna Reid had told GMB viewers that it looked as if Covid-19 self-isolation could be cut to five days to ease the staffing crisis in places such as the NHS and schools.
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Dr Hilary said: "Well if you shorten the period of self-isolation you'll certainly get more people back to work that week. Two weeks later, you'll have less.
"It's as simple as that because you will have 30% of people still infectious after five days... going back to work, passing on the virus to their work colleagues.
"After seven days, it's 16% so a significant difference.
"You can't keep cutting self-isolation just because it's convenient. There's a reason for it.
"Scientists are saying keep it at seven days. The economists are saying let's shorten it or get rid of it all together."
Dr Hilary also stressed that Omicron was causing problems in the NHS, reports Wales Online.
And he spoke out against herd immunity, said we were still flattening out the curve and trying to allow the NHS to cope.
He added: "You can't say just because it's milder, let's forget everything we are doing, and let it spread around the community so we've got herd immunity.
"We're still flattening the curve., trying to allow the NHS to cope. We want less people infected all at once.
"Ultimately, probably everybody will get Omicron, vaccinated or not.
"But people will have it less severely if they are vaccinated with all three jabs and we'll have less people in hospital and the NHS will be able to cope."
