Despite soaring cases and record-high Covid-19 hospitalizations, the United States is approaching the "threshold" of transitioning to living with the coronavirus as a manageable disease, Anthony Fauci said Tuesday.

Speaking to the Center for Strategic and International Studies (CSIS), the top US scientist said eliminating Covid was unrealistic and that "Omicron, with its extraordinary, unprecedented degree of efficiency of transmissibility, will ultimately find just about everybody."

"There's no way we're going to eradicate this" virus, he said, given its contagiousness, its propensity to mutate into new variants and the large pool of unvaccinated people.

Those up to date with their vaccines remain well protected against severe outcomes, but vaccine efficacy against infection has fallen.

But "as Omicron goes up and down," the country will hopefully enter a new phase "where there'll be enough protection in (the) community, enough drugs available so that when someone does get infected and is in a high risk group, it will be very easy to treat that person," said Fauci.

"When we get there, there's that transition, and we may be on the threshold of that right now," he said, while also stressing that with the country currently recording almost a million infections a day, nearly 150,000 people in hospital and more than 1,200 daily deaths, "we're not at that point."

Official data showed there are currently 145,982 Covid hospitalizations, even though a significant percent are thought to be hospitalized "with" the disease rather than because of it.

Earlier, the 81-year-old director of the National Institute of Allergy and Infectious Diseases slammed vaccine skeptic Republican Senator Rand Paul for unleashing "crazies" who were threatening his life and harassing his family, in unusually emotional congressional testimony.

President Joe Biden's top officials, including his chief medical advisor Fauci, Centers for Disease Control and Prevention (CDC) director Rochelle Walenksy and acting Food and Drug Administration (FDA) head Janet Woodcock were summoned to testify before the Senate about the pandemic.

While many fellow lawmakers focused their questions on the lack of adequate testing and confusing new guidelines on how infected people should end their isolation, Paul, who has railed against vaccine mandates and refused to get vaccinated, said Fauci was personally to blame for people's deaths.

Top US scientist Anthony Fauci said personal attacks by Senator Rand Paul distracted from the important work of tackling the pandemic, and made him a personal target for violence
Top US scientist Anthony Fauci said personal attacks by Senator Rand Paul distracted from the important work of tackling the pandemic, and made him a personal target for violence POOL via AFP / Greg Nash

Paul faulted Fauci for hundreds of thousands of deaths that occurred since Biden took office -- although the vast majority of those fatalities were unvaccinated and health officials, including Fauci, have consistently advocated for vaccines.

"You personally attack me and with absolutely not a shred of evidence of anything you say," Fauci responded.

"All of a sudden that kindles the crazies out there and I have life threats upon my life, harassment of my family and my children with obscene phone calls."

Fauci recalled that in late December, a man was arrested on his way from California to the capital Washington armed with an AR-15 assault weapon and multiple rounds of ammunition.

The man said he wanted to kill Fauci, because of what he said was blood on the scientists' hands.

Fauci then brandished a printout from Paul's website that showed the banner "Fire Dr Fauci" next to an invitation to donate to the Republican's campaign.

Though Omicron causes severe cases at a lower rate than Delta, it is reaching more people because of its extreme infectiousness.

By December 27, the age-adjusted vaccine efficacy against hospitalization was 92 percent, according to data from New York state.