Omicron could become the dominant variant worldwide, experts say, but they still don't know how harmful it is

• The Omicron variant could become dominant worldwide within weeks, one expert has said.
• Others, including Dr. Anthony Fauci, have been more cautious about making predictions with the information available.

Experts have said the new Omicron variant could soon become the most common COVID-19 variant worldwide — but it's still unclear how harmful it is.

Devi Sridhar, chair of global public health at Edinburgh University, told Channel 4 Monday, that Omicron is likely to replace the Delta variant as the dominant strain across the world. "It's a matter of weeks right now, I think, until we reach that point," she told the broadcaster.

Dr. Jacob Lemieux, who monitors variants for a research collaboration led by Harvard Medical School, told Global News Tuesday that it was "still early days" in terms of determining whether Omicron will become dominant. "But increasingly, data is starting to trickle in, suggesting that Omicron is likely to outcompete Delta in many, if not all, places," he said.

The Omicron variant has 32 mutations in an unusual combination in the part of the virus that attaches to human cells. It's fast-spreading in South Africa and experts are racing to find out if its mutations make it more infectious, more deadly, or better at evading vaccines than the Delta variant.

Delta, which itself is a mutated form of the original virus, was picked up on nearly all sequenced COVID-19 lab tests worldwide in November, the World Health Organization said in its latest COVID-19 update.

Dr. Anthony Fauci, president Joe Biden's chief medical adviser, told CNN's State of the Union Sunday that Omicron was "clearly" becoming dominant in South Africa. Insider reported Tuesday that Omicron had driven a 400% increase in infections in two weeks in South Africa.

But some experts have cautioned that Omicron's rapid spread in South Africa, which had low levels of Delta and a largely unvaccinated, young population, may not be replicated elsewhere.

Robin Colgrove, assistant professor of medicine at Harvard Medical School, told WCVB Monday that drawing comparisons with South Africa wouldn't necessarily help determine the path of the variant in the US due to differing conditions in the two countries. "Vaccination levels are different and transmissions are different," he said.

In the US, Fauci said that there was "an indication" that Omicron —which has now been detected in 18 states — was spreading in the community. The question for the US is what happens when Delta and Omicron compete against each other, Fauci said.

Fauci said in a press briefing Friday that as more COVID-19 cases caused by Omicron occur, the Centers for Disease Control and Prevention will be able to calculate whether it might become dominant in the US.

Matthew Binnicker, director of clinical virology at Mayo Clinic in Rochester, Minnesota told Global News Tuesday that the US would know whether Omicron will replace Delta in "about two weeks".

"It'll be really interesting to see what happens when more infections potentially occur in older adults or those with underlying health conditions," he said.

The experts, including Fauci, cautioned that the implications of Omicron becoming dominant are unclear and will remain so until more case data is available.

"It's going to take a while for us to know what the impact is going to be globally," Fauci said in Friday's briefing.

Paul Hunter, professor of medicine and specialist in medical microbiology, told BBC Breakfast on Monday that "the big remaining question is actually how harmful it is if you do get COVID-19 with this Omicron variant," per multiple media outlets.

"That's the question that we're struggling to answer at the moment," Hunter said.