As the omicron variant continues to spread throughout the world, new modeling data shows the latest strain may cause millions more new infections per day in the U.S. but fewer hospitalizations and deaths compared to the delta variant.
Researchers at the Institute for Health Metrics and Evaluation at the University of Washington’s School of Medicine revised its COVID-19 modeling to include updated information about the omicron variant.
They found the U.S. may see a total of about 140 million new infections from Jan. 1 to March 1, 2022, peaking in late-January at about 2.8 million new daily infections.
“We are expecting an enormous surge in infections … so, an enormous spread of omicron,” IHME director Dr. Chris Murray said Wednesday. “Total infections in the U.S. we forecast are going from about 40% of the U.S. having been infected so far, to having in the next 2 to 3 months, 60% of the U.S. getting infected with omicron.”
While meta-analyses have suggested previous variants cause about 40% of cases to be asymptomatic, Murray said more than 90% of people infected with omicron may never show symptoms.
Researchers estimate that out of the millions of projected new daily infections, only about 400,000 cases may be reported, as most Americans infected with the virus won’t feel sick and may never get tested. At the peak of last year’s winter surge in January, the country was reporting a little over 250,000 new cases per day.
The country has reported about 51 million confirmed cases since the pandemic began, according to Johns Hopkins data.
Outside the U.S., models show the world may see approximately 3 billion new infections in the next two months with peak transmission occurring in mid-January at more than 35 million new cases per day.
Murray says the forecast may be pessimistic, but other health experts say it is within the realm of possibility based on the early, incomplete information on  omicron.
“Sure, this a potential outcome,” said Julie Swann, professor at North Carolina State University who studies pandemic modeling and health systems. “How certain am I that this is the outcome? Not certain at all.”
While infections are expected to skyrocket, the IHME model shows hospitalizations and deaths will be about the same. Researchers found the infection-hospitalization rate of omicron is about 90% to 96% lower than delta, and the infection-fatality rate is about 97% to 99% lower.
“In the past, we roughly thought that COVID was 10 times worse than flu and now we have a variant that is probably at least 10 times less severe,” Murray said. “So, omicron will probably … be less severe than flu but much more transmissible.”
A study of real-world data published Wednesday by the Imperial College of London suggests that omicron cases have up to a 20% reduced risk of any hospitalization compared to the delta variant, and up to a 45% reduced risk of admitted overnight.
But some health experts say it’s too soon to speculate on omicron’s severity. Other models have shown hospitalizations may exceed last winter’s surge, Swann said.  
“With omicron, we are seeing lots of infections, we are already seeing hospitalizations and – even though it takes time to die – we are already seeing deaths,” said Dr. Daniel Griffin, chief of infectious diseases at ProHealth Care and a clinical instructor of medicine at Columbia University. “It will take a little more time to know for certain about any relative severity as well as cross protection for reinfection with other variants after omicron infections.”
The nation’s top infectious disease specialist, Dr. Anthony Fauci, said at a Wednesday news briefing that omicron may be less dangerous than previous variants. “That’s conceivable,” he said, “but you don’t want to count on it.”
IHME researchers don’t expect to update the models before the second week of January as the holidays tend to delay the data, Murray said. But he said the modeling showed the biggest impact on transmission was masking, particularly if 80% of the population wore high-quality masks.
He also highlighted the importance of vaccinations and boosters, although the models showed boosters didn’t have a significant impact on transmission because of waning immunity after six months. 
“Vaccination and boosters are really important,” Swann said. “But we have to get them soon because omicron spreads so quickly that once cases and hospitalizations go up, additional vaccination has less impact.”
Contributing: Karen Weintraub, USA TODAY. Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT. 
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

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