"When you talk about whether or not Omicron - because it's a highly transmissible but apparently not as pathogenic one, for example as Delta - I would hope that is the case," said the director of the National Institute of Allergy and Infectious Diseases. said Monday.
"But that would only be the case if we did not get another variant that evades the immune response to the previous variant," Fauci told Davos Agenda, a virtual event being held this week by the World Economic Forum.
"We were lucky" that Omicron did not share some of the same characteristics as Delta, "but the large amount of people getting infected overrides the somewhat lower level of pathogenicity," Fauci said.
"It's an open question as to whether Omicron will be the live virus vaccination that everyone is hoping for because you have so much variety with new variants popping up," he said.
Schools struggling with the Omicron rise
Several districts in Northern Virginia and the Metro Richmond area have announced they will reject the latest order, which is set to begin on January 24th.
"Our layered prevention strategies have proven effective in keeping transmission rates low in our schools," Fairfax County Public Schools Superintendent Scott Brabrand said in a letter to the school community.
"Universal masking has been shown to be effective in keeping Covid-19 transmission rates low in our schools and ensuring that schools remain safe and open," a statement from Arlington Public Schools said of its decision.
In Texas, all schools and offices in the Houston Independent School District will be closed Tuesday due to rising community cases, the school district announced on its website. Teaching is expected to resume on Wednesday.
The school district urged students and staff to take "this extra day to mitigate potential exposure."
Progress with future vaccines is moving forward
To further advance variants, new vaccines are under development.
Moderna should have data available on its Omicron-specific Covid-19 vaccine in March, the company's CEO Stephane Bancel said on Monday.
"It should be in the clinic in the coming weeks. And we hope in the March timeframe that we should be able to have data to share with regulators to figure out the next step forward," he said in a panel discussion in Davos.
A combined Covid-19 and flu booster shot from Moderna may also be available in some countries in the fall of 2023, Bancel said, but warned that the date was a "best case scenario."
Vaccine doses remain the most effective way to avert serious complications, which remain a factor in the nation's recovery as Americans continue to die from Covid-19. The average number of deaths has exceeded 1,600 daily over the past week, according to JHU data.
Booster doses have successfully demonstrated the ability to raise an individual's antibody levels months after initial inoculations, helping to keep them at higher risk out of the hospital.
In December, Israel began testing a fourth dose of coronavirus vaccines for healthy participants ahead of a rollout of the extra booster shot for at-risk populations - marking the first study of its kind among healthy people receiving a fourth dose.
"I think the decision to allow the fourth vaccine to vulnerable populations is probably the right one," said Dr. Gili-Regev Yochay, director of the Infection Prevention Control Unit at Sheba Medical Center, on Monday about the data. "It may provide a little bit of benefit, but probably not enough to support the decision to give it to the entire population, I would say."
CNN's Jacqueline Howard, John Bonifield, Virginia Langmaid, Dan Merica, Eva McKend, Ryan Nobles, Livvy Doherty, Carma Hassan, and Alex Medeiros contributed to this report..