Almost 73 per cent of US adults are fully vaccinated against coronavirus. (File)
A testing requirement may be added to last week's move by the US to shorten the isolation period for some people who test positive for Covid-19, Anthony Fauci said.
The US Centers for Disease Control is considering adding a negative test to recommendations on a shortened isolation period for people with asymptomatic infections, President Joe Biden's chief medical adviser said on ABC's "This Week."
That could make having easy access to tests a flashpoint at a time many Americans are struggling to obtain them.
Last week, US health officials cut the recommended isolation time to five days from 10 after after a positive test. Fauci acknowledged "pushback" to the shortened span without any further test that might indicate if a person is still infected.
"We're going to be hearing more about that in the next day or so from the CDC," he said on ABC.
On CNN, Fauci said the omicron variant now sweeping the US may cause milder illness for most, but the sheer number of cases is likely to cause serious sickness in many unvaccinated Americans, and strain health-care resources. "This is a much, much more transmissible virus than Delta is," he said.
Hospital admissions from Covid are rising again in the US, and average daily infections are at a record 400,000, Fauci said.
Several states have mobilized their National Guards to help provide medical care amid staffing shortages and, like Texas, asked for federal help.
Studies in the UK have shown that the omicron strain appears less severe than the delta variant it supplanted. South Africa, where the new variant was identified in November, said last week the omicron-driven wave appears to have passed its peak without a notable rise in deaths.
Almost 73 per cent of US adults are fully vaccinated, and 36.3 per cent have received a booster shot, according to data from the US Centers for Disease Control and Prevention. But coverage varies widely between states.
Fauci said that despite omicron's rapid spread, schools should remain open, though with masking and other rules, and he urged parents to get eligible children vaccinated.
Mitigation strategies including masking and vaccines are working in schools, which should remain open if possible, US Education Secretary Miguel Cardona said Sunday.
"Our default should be in-person learning," Cardona said on CBS's "Face the Nation," citing the benefits of classroom education over virtual learning.