Two years into the coronavirus pandemic, the United States is confronting another dark winter, with the Omicron variant threatening to worsen an already dangerous surge of cases.
Hospital admissions for Covid-19 have jumped 45 per cent over the past month, and confirmed cases have increased 40 per cent to a week-long average of 123,000 new US infections a day, according to a Reuters tally.
Pfizer, one of the chief vaccine makers, on Friday predicted the pandemic would last until 2024 and said a lower-dose version of its vaccine for children aged 2 to 4 generated a weaker-than-expected immune response, which could delay authorisation.
The National Football League rescheduled three weekend games after multiple teams were hit hard by outbreaks.
The National Hockey League added another game to its recent list of postponements, heightening doubts about the league's plan to send the world's top players to the Beijing Olympics in February.
In New York, Radio City Music Hall announced it has cancelled all remaining dates of the Rockettes' annual Christmas Spectacular "due to increasing challenges from the pandemic", after staging more than 100 shows over the past seven weeks.
The Omicron variant appears to be far more transmissible than previous iterations of the virus, and more agile in evading immune defences, according to early studies.
Booster shot campaign
Public health officials say it is likely to become the dominant variant in the country, following fast-moving spreads in countries such as South Africa and the United Kingdom, and could strain hospitals still struggling to contain this summer's Delta variant surge.
"GET BOOSTED NOW. Tidal wave of Omicron likely coming to a hospital near you soon," Dr Tom Frieden, former chief of the Centres for Disease Control and Prevention (CDC), posted on Twitter.
Preliminary data in South Africa suggests Omicron leads to milder illness than the Delta variant, which is still driving much of the current wave of infections. But a British study released on Friday found no difference in severity between the two variants.
Either way, Omicron's extraordinary level of infectiousness means it could cause many additional deaths, the top US infectious disease expert, Dr Anthony Fauci, said on Friday.
"When you have a larger number of people getting infected, the total amount of hospitalisations is going to be more. That's just simple math," Dr Fauci told CNBC.
Dr Fauci also said officials are discussing whether to redefine what it means to be "fully vaccinated" to include booster shots.
The latest surge is creating yet another round of disruptions to daily life, although widespread lockdowns of workplaces and social gatherings have not yet been put in place.
A federal appeals court on Friday reinstated a nationwide vaccine-or-testing Covid-19 mandate for large businesses - an Occupational Safety and Health Administration (OSHA) rule that covers 80 million American workers.
Some Americans have reconsidered holiday plans. Winifred Donoghue, a New York City advertising writer, cancelled a January 8 disco party at her family's vacation home in Highland Lakes, New Jersey, that was intended to be both a 60th birthday and New Year celebration.
"Two weeks ago, everyone was boosted. Then the infections went up exponentially," she said. "By January, who is going to feel safe? I just pulled the plug on it."
Eric Hrubant, the chief executive of CIRE Travel, said he hadn't yet seen a wave of cancellations, as he did in August when the Delta variant swept the country. But worried clients have inundated the agency with calls about new Covid-19 protocols, such as mandatory travel quarantines.
"People aren't panicking," he said. "People are making educated decisions."
Several states have hit alarming levels of cases and hospitalisations. The US states reporting the highest seven-day average of infections were New York, Ohio, Pennsylvania, Illinois and Michigan, according to a Reuters tally.
In Ohio, exhausted hospital workers will be getting some help starting on Monday from 1,050 National Guard troops – including 150 nurses, emergency medical technicians and others with medical training, Governor Mike DeWine said on Friday.
The CDC released a new "test-to-stay" strategy on Friday that allows unvaccinated children to remain in school, even if they are exposed to the virus.
The protocol is intended to replace automatic quarantines, which have required tens of thousands of students to miss school days.