WASHINGTON — The omicron variant of the coronavirus will likely be less severe than the delta variant, which remains the “real problem” for Americans this winter, Dr. Anthony Fauci said Thursday.

In an interview, Fauci said the country is “already seeing a resurgence of cases” and warned that 60 million Americans remain unvaccinated.

“I think we have enough problems with delta,” said Fauci, President Biden’s chief medical adviser and head of the National Institute of Allergy and Infectious Diseases.

“People keep talking about a winter wave with omicron – we’re still getting over 100,000 cases a day,” he said, referring to the delta variant. “We have around 50,000 people in the hospital. We have close to 1,400 deaths per day. I think we really better focus on what our real problem is, and our real problem is delta right now.”

Anticipating a winter surge in COVID-19 cases, Fauci said it was “inexplicable” that such a large portion of the population has not gotten vaccinated.

“It’s really unfortunate and a sad commentary on our country that we have a historic outbreak that has already killed over 780,000 Americans, and at least 5 million and maybe twice that amount globally, and for reasons that are inexplicable – but may be explainable by political ideology – that we have people who are refusing to get vaccinated,” he said. “We have 60 million people in this country who refuse to get vaccinated. I mean, that is really very disturbing.”

Omicron was first identified in South Africa last month, alarming public health experts and governments that the highly mutated variant could prove more transmissible, cause more severe disease and more readily evade immunity provided either by previous infection or vaccines.

Fauci said that data from South Africa is still preliminary, but “suggests very strongly that omicron has a transmission advantage.”

While omicron does appear more capable of evading existing immunity than delta, which dominates cases worldwide, Fauci said that data released from Pfizer and BioNTech this week on the effectiveness of three doses of their COVID-19 vaccine against omicron was “good news.”

Hospitalization rates in South Africa are also providing early indications that omicron is less severe.

“Indications from South Africa suggest that it is at least not more severe, and likely is going to be less severe – and I say likely with a big caveat that we still have a lot more to learn,” he said. “When you look at the ratio between cases and hospitalizations, the ratio of hospitalizations to cases is much smaller than what it was previously. The duration of hospital stay is much less, indicating a strong suggestion that it’s less severe.”

Some epidemiologists believe the emergence of a variant that is less deadly but more contagious could ultimately precipitate the end of the pandemic. But Fauci approached that perspective with caution.

If omicron turns out to be less severe, but much more transmissible, “at the end of the day the number of people with severe disease might end up being the same,” he said.

“If it really is much more transmissible, just the quantity alone of people getting infected could outbalance the positive nature of it being less severe,” he added. “If you have something that has a small level infection and a high degree of severity, that might be equivalent to something that has a wide degree of infection and a small degree of severity.”

But Fauci said the demographics of South Africa, where scientists are still getting their best data on omicron, are too different from the United States to draw direct comparisons. Omicron has become dominant there but that does not necessarily mean the same will happen in the United States, he said, pointing to the Beta variant, which caused a huge wave of cases in South Africa but barely registered here.

He also dismissed reports that omicron has picked up a genetic piece of the common cold.

“I think it’s too early to say anything about that – that’s pure speculation,” he said. “I have no idea what that means.”

Omicron has been identified in more than 57 countries, including in the United States.

With the variant already here, Fauci said he did not think vaccine requirements for domestic airline travel would be necessary.

“I don’t think it’s particularly serious,” he said of discussions on vaccine requirements for domestic flights. “You want to have safe flying, and the safe way to fly is wear a mask when you’re in the airport. And you have to by regulation when you’re on the plane.”

He said he wants to see travel bans that were imposed on southern African nations days after omicron was identified there lifted “very soon.”

“It was an emergency measure that we did,” Fauci said, “and I would hope that we could turn that around as quickly as possible.”