Omicron Could Surge in U.S. Soon, C.D.C. Warns

The proportion of coronavirus cases in the United States caused by the Omicron variant has increased sharply, and may portend a significant surge in infections as soon as next month, according to new data from the Centers for Disease Control and Prevention.

During the week that ended on Saturday, Omicron accounted for 2.9 percent of cases across the country, up from 0.4 percent in the previous week, according to agency projections released on Tuesday.

In the region comprising New York, New Jersey, Puerto Rico and the U.S. Virgin Islands, the percentage of Omicron infections had already reached 13.1 percent.

In a briefing on Tuesday with state and local health officials and representatives of public health labs across the nation, C.D.C. officials warned of two possible scenarios. The first was a tidal wave of infections, both Omicron and Delta, arriving as soon as next month, just as influenza and other winter respiratory infections peak.

“The early signals say there are going to be waves coming,” said Scott Becker, chief executive officer of the Association of Public Health Laboratories, who was on the call.

“We are already expecting an uptick, just because we have seen a lot of respiratory viruses already this fall, including R.S.V., which was extensive,” he added.

Federal health officials also proposed a second scenario in which a smaller surge in Omicron cases occurs in the spring. It was unclear which forecast was more likely.

Early evidence about the variant has only begun to emerge, and it remains unclear how often infections with Omicron lead to hospitalizations or deaths. The variant seems able to partly dodge the body’s immune defenses, but scientists have not yet determined to what degree vaccination and prior infection may safeguard individuals from severe disease.

To track variants, the C.D.C. uses a national surveillance system that collects samples, as well as genetic sequences generated by commercial laboratories, academic laboratories and state and local public health laboratories.

The U.S. system was relatively slow to pick up cases of the variant, perhaps in part because of travel patterns or restrictive U.S. entrance rules. But the system is also constrained by blind spots and delays.

Last week, the C.D.C. reported that of the 43 known infections detected in the United States in the first eight days of December, 34 of the patients, or 79 percent, had been fully vaccinated when they first started showing symptoms or tested positive. Only about a third of the 43 people had traveled internationally in the two weeks before diagnosis, indicating some level of community spread of the variant.

The fight against Omicron may require the federal government to replenish funding for the response, the secretary of health and human services, Xavier Becerra, suggested on Tuesday. Mr. Becerra told reporters that about $10 billion was left of the $50 billion Congress had allocated for testing.

For public health labs, as for hospitals, staffing may be a challenge, Mr. Becker said.

“It’s the same staff who do molecular testing and genomic sequencing and flu surveillance,” he said. “We’re stretched already, so we have to begin to think about alternative plans, temporary staffing, bringing in people who helped during surge events last year.”

“The lab community is tired,” Mr. Becker added. “The health care community is tired. ‘Gear up, we may have another surge,’ is a tough message to hear.”

In Europe, health officials have warned of a spike in Omicron cases. According to estimates on Monday, cases of the variant in Denmark, which is similar to the United States in terms of vaccination rates and average age, were doubling every two days.

Dr. Tedros Adhanom Ghebreyesus, the director general of the World Health Organization, said in a news briefing on Tuesday that “Omicron is spreading at a rate we have not seen with any previous variant.”

Dr. Tedros and senior W.H.O. officials cautioned against underestimating the variant. “Even if Omicron causes less severe cases, the sheer number of cases could once again overwhelm unprepared health systems,” he said.

In the United States, state and local health officials urged Americans to take steps to prevent the spread of Covid by getting vaccinated, getting booster shots and wearing masks in public indoor settings. Families and friends gathering for the holidays must get tested before celebrating together, gathering outside if possible or, if not, in well-ventilated spaces.

“As the Delta variant continues its rapid spread in the U.S., state and territorial health leaders are becoming increasingly concerned about emerging data from Europe and South Africa that indicate the Omicron variant may be even more transmissible,” said Michael Fraser, chief executive officer of the Association of State and Territorial Health Officials.

“Hospital capacity is already at a breaking point in many states because of severe cases of Covid-19,” he added.

Nick Cumming-Bruce contributed reporting.

Governors from five states have written a joint letter to Lloyd J. Austin III, the defense secretary, asking that their National Guard troops be exempted from a federal coronavirus vaccine mandate, greatly escalating what had been a single state conflict over inoculations.

“Setting punishment requirements for refusing to be Covid-19 vaccinated, and requiring separation from each state National Guard if unvaccinated are beyond your constitutional and statutory authority,” wrote the governors of Alaska, Wyoming, Iowa, Mississippi and Nebraska, all Republicans, to Mr. Austin, and asked that their states be given an exemption from the requirement. The Pentagon has yet to respond to the letter, which was dated Tuesday.

Last month, the Defense Department rejected an attempt by Kevin Stitt, the governor of Oklahoma, to exclude the state’s National Guard from the mandate, setting the stage for Guard members in the state to lose their jobs should they refuse. The department this week released a new order noting that all guard members who do not get vaccinated will receive a general order of reprimand, which would essentially end their career.

Federal officials have said that governors have no legal standing to allow Guard members to refuse the vaccine mandate. State officials and some legal experts, however, believe that unless National Guard members are federally deployed, they are under the jurisdiction of the governor of their state and therefore not subject to federal mandates.

Roughly 97 percent of the 1.3 million active-duty service members in the United States have had at least one dose of a vaccine, but the numbers are much lower for members of the Guard and Reserve.

Each service branch has a different deadline for shots, and the Guard units will not face theirs for months. By increasing the number of states tangling with the department, the governors of the states that have generally resisted vaccine mandates underscore the increasing politicization of the mandates in a part of government — the military — where vaccine mandates are frequent and largely without controversy.

The Air Force, with more than 325,000 active duty members, was the first to hit the deadline; a mere 27 airmen — all with less than six years of service — are the first believed to have been fired over vaccine refusals, Pentagon officials said this week. The Army and Navy are expected to announce their numbers imminently.

The Defense Department has granted very few exemptions from the mandate, other than to people who were already leaving the military or those who have medical issues. So far, not a single service member has been granted a religious exemption.

The school board in Los Angeles decided on Tuesday to put off until the next academic year a plan to require coronavirus vaccination for students 12 and older who attend class in person.

Under a plan that the Los Angeles Unified School District’s Board of Education approved in September, those students would have needed to show proof of full vaccination by Jan. 10. Otherwise they would be transferred to an online study program.

But on Tuesday, the board voted to delay the policy’s start date until the fall 2022.

When the district first announced the vaccine mandate, about 80,000 students who were eligible for vaccination had not yet been inoculated. As of last week, the figure was about 34,000, The Los Angeles Times reported.

The school district said on Tuesday that delaying the rule would allow further time to “offer educational opportunities” to vaccine-hesitant families. It also said that more than 86 percent of students in the district had already complied with the mandate, and that others were in the process of registering their vaccine paperwork.

Starting in January, the district will require all staff members and students to undergo weekly coronavirus testing, the district said on Tuesday. Beginning in February, only unvaccinated students will have to be tested regularly.

Los Angeles schools serve more than 600,000 students, making the school district the nation’s second largest. The vaccine mandate would apply to about 460,000 of them, including students at independent charter schools using the district’s buildings.

In New York City’s public school system, the nation’s largest, a vaccine mandate for most employees compelled tens of thousands of Department of Education employees to get at least one dose. Mayor Bill de Blasio said in September that the city’s focus for the time being would be on getting students back into classrooms, not on requiring them to be vaccinated.

The city did, however, require students who take part in activities in which the risk of spreading the virus is high — including playing basketball, football or volleyball — to get at least one dose by their first day of competitive play. Los Angeles schools require vaccination for any school-sponsored extracurricular activity, including sports, drama and music.

The state of California has also imposed a vaccine mandate for students that could take effect as soon as next fall, adding the coronavirus to the list of diseases that students must be vaccinated against, like measles and mumps. But the state mandate is contingent on the Food and Drug Administration granting the vaccines full approval for pediatric use, and not just the emergency use authorization that is now in effect.

A new study looking at blood samples from people who received two doses of a Covid-19 vaccine made by the Chinese pharmaceutical company Sinovac suggested that the vaccine would be unable to prevent an infection of the new, highly infectious Omicron variant.

The research, which analyzed the blood of 25 people vaccinated with Sinovac, is the latest sign of the new challenge Omicron presents as it spreads across the world. The scientists from the University of Hong Kong found that, in laboratory experiments, none of the 25 samples produced sufficient antibodies to block the variant from invading cells. The researchers said it was not yet clear whether a third shot of Sinovac would improve the results.

The studies are preliminary, and antibody levels do not give a complete picture of a person’s immune response. It is unclear whether the Sinovac vaccine can fend off severe disease or death from Omicron, but it most likely offers some protection.

Sinovac said in a statement Wednesday that while two doses of its vaccine were much less effective against Omicron, three doses might prevent infection with the variant.

The study also examined blood from 25 people vaccinated with the Pfizer-BioNTech vaccine and found less than one-quarter of the subjects produced antibodies that could neutralize Omicron. These results were consistent with what other studies have found.

The researchers advised the public in Hong Kong to get a third dose of vaccine as soon as possible, though they did not specify which kind.

If the results are accurate, they could spell particular trouble for China, where the vaccine is commonly used. China has vaccinated more than 1 billion of its citizens, mostly with Chinese vaccines, but has relied largely on strict lockdowns and quarantines to curb the spread of the virus. Other studies have also found disappointing results with Sinopharm, the other major vaccine in China.

In recent weeks, Chinese officials have indicated that the country’s vaccination levels are approaching what they said would be required for herd immunity. However, Sinovac’s weakness against the new variant, two cases of which were detected this week in two Chinese cities, could signal that the country’s lockdowns and closed borders will persist.

Beginning in September, parts of the country began to offer booster shots, and now the extra shot is widely available. This month a top Chinese official called for an acceleration in plans to give booster shots to older adults. In Tianjin, where one of China’s two confirmed Omicron cases was found, state media wrote in a Wednesday article that “there should be no delay in getting boosters.”

Even so, far fewer people have had boosters. As of Dec. 10, 120 million people in China have had a third vaccine dose, far short of the 1.16 billion who have had two, according to state media.

KUALA LUMPUR, Malaysia — Secretary of State Antony J. Blinken cut short his trip to Southeast Asia on Wednesday after a journalist traveling in his delegation tested positive for the coronavirus.

A State Department spokesman said Mr. Blinken has tested negative at every stop on diplomatic visits over the past week to Britain, Indonesia and Malaysia. He had scheduled meetings for Thursday with senior officials in Bangkok, the Thai capital, but canceled to return to the United States.

Ned Price, the State Department spokesman, said Mr. Blinken had called the Thai deputy prime minister, Don Pramudwinai, to “express his deep regret” over the change in plan.

“He explained that in order to mitigate the risk of the spread of Covid-19 and to prioritize the health and safety of the U.S. traveling party, and those they would otherwise come into contact with, the secretary would be returning to Washington, D.C., out of an abundance of caution,” Mr. Price said in a statement as the delegation was leaving Kuala Lumpur.

The journalist who tested positive for the virus was part of the small group of news media personnel who travel with the secretary of state. The journalist, who was not identified for privacy reasons, tested negative in Jakarta on Monday but then received a positive test for the virus after arriving in Kuala Lumpur, the Malaysian capital, on Tuesday night.

Mr. Price said the journalist who tested positive would remain in Kuala Lumpur for mandatory isolation while the rest of Mr. Blinken’s entourage traveled on.

Foreign governments have stepped up testing requirements for traveling diplomatic delegations as the Delta and Omicron variants have surged around the world.

Sanofi, the French pharmaceutical company, said on Wednesday that its once highly anticipated Covid vaccine produced strong immune responses in vaccinated volunteers who received a single dose of the shot as a booster.

The data suggest that the shot, which is still in development and not authorized anywhere in the world, could eventually be used in booster campaigns after it failed to fulfill initial expectations that it would become one of the most important weapons in the fight against the virus. Still, Sanofi has yet to finish a key clinical trial that it said would need to generate results before regulators around the world consider authorizing the shot.

Sanofi said that study participants who received the company’s shot as a booster saw large increases in their levels of neutralizing antibodies, which are one subset of the expansive immune response prompted by vaccines. The more than 500 volunteers had been fully vaccinated between four and 10 months earlier with either Johnson & Johnson’s single-shot vaccine or two shots of the vaccines from Pfizer, Moderna or AstraZeneca.

The antibody responses generated by using the Sanofi shot as a booster were comparable to those seen with a boost of the Pfizer shot in a separate study that compared seven different vaccine brands.

Sanofi said that laboratory testing is underway to see if the vaccine might work against the fast-spreading Omicron variant. The company said that scientists are using blood samples from volunteers in the booster study to see how their vaccine-generated antibodies fare against the Omicron variant.

Sanofi is still waiting for results from a large Phase 3 study that will assess the safety and efficacy of its vaccine. Those results were supposed to come in the latter part of this year. But Sanofi said on Wednesday that too few volunteers in its trial have gotten sick with Covid, delaying the results until early next year.

In the past, the Food and Drug Administration has wanted to see results from Phase 3 trials on previously unvaccinated volunteers before considering a vaccine as a booster. But the agency has updated its requirements during the pandemic to bring vaccines more quickly into use.

Sanofi said in a news release that it planned to file its booster data with regulatory authorities after it has Phase 3 trial results.

Sanofi’s shot uses a more conventional approach than that deployed in other, more swiftly developed Covid vaccines. It triggers immunity using a version of the coronavirus’s spike protein that was synthesized in a laboratory using engineered viruses that grow inside insect cells. Sanofi led the development of the shot with help from GlaxoSmithKline, which supplied an adjuvant, an ingredient commonly used in vaccines meant to boost the immune response.

In the early months of the pandemic, the vaccine was one of six selected for funding from Operation Warp Speed, the Trump administration’s effort to accelerate vaccine development.

But the vaccine hit a major setback a year ago, when its developers announced that a miscalculation in the manufacturing process had resulted in volunteers being given lower doses than planned and that plans for the Phase 3 study would have to be delayed.

International students and skilled workers returned to Australia for the first time in 21 months, as the country eased some coronavirus restrictions, even as health authorities predicted a sharp increase in the number of Omicron cases.

Visa holders, who had been shut out of Australia since March 2020 when noncitizens were banned from entering the country, arrived in Melbourne and Sydney on Wednesday. On the same day, the island state of Tasmania fully opened its borders to other Australian states for the first time since the start of the pandemic.

The authorities have been loosening restrictions ahead of the holidays despite surging case numbers in the states of New South Wales and Victoria, as well as concerns that any outbreaks might overwhelm health systems in states that have been largely free from the coronavirus.

In New South Wales, an outbreak stemming from a nightclub event has swelled to over 200 cases since it was first detected six days ago, the authorities said on Wednesday. Nearly 700 people attended the 1970s prom night themed event on Dec. 8. Overall, the state reported 1,360 new cases on Wednesday, compared with 804 the previous day.

The state is seeing a “very substantial increase” in infections of both the Omicron and Delta variants, Brad Hazzard, the state’s health minister, said at a news conference. He warned that based on scientific modeling, the state could see 25,000 new coronavirus cases a day by the end of January.

At the same time, the state lifted numerous pandemic restrictions. Officials said masks were no longer mandatory in most settings and unvaccinated residents, who had been barred from restaurants, gyms and retail stores, would now have the same freedoms as vaccinated residents.

In the state of Victoria, 700 people are in quarantine after a resident who visited two nightclubs on Friday tested positive for the coronavirus. Still, that state also announced a similar easing of restrictions.

While most states eased restrictions, coronavirus-free Western Australia tightened its border rules, announcing it would bar residents of New South Wales from entering the state apart from in exceptional circumstances. The state will be the last to open to the rest of the country, with its hard border expected to lift on Feb 5.

It’s a strange time to work for Omicron Granite & Tile in Ohio. Or Omicron Sensing, an electrical manufacturer in Mumbai. Or the Omicron Family Restaurant in Wisconsin. And then there’s being a member of one of the various fraternities, sororities and honor societies whose names feature an “Omicron” — maybe more so if there’s also a “Delta” in there.

In May, the World Health Organization announced that it would start naming certain variants of the coronavirus after Greek letters. “Delta” is easier to remember than B.1.617.2. But if your business has an “Omicron” in its name, you might wish more people were talking about the B.1.1.529 variant.

The question is, do you embrace the connection?

Some organizations are meeting the naming overlap with benign curiosity or humor.

Tara Singer, the president and chief executive of the Omicron Delta Kappa honors society, said she was not concerned about the public relations impact of the Omicron variant on her organization. “Delta Air Lines weathered this well, so we will, too,” she said in a phone interview.

The Omicron Family Restaurant in West Bend, Wis., is taking the double puns of Omicron and Corona one step further. Last Friday, it began offering a bottle of Corona beer with a T-shirt that reads, “I Got Corona at Omicron” for $15.

HALIFAX, Nova Scotia — In early November, I flew to southern Africa to report a series of stories about the state of the Covid-19 pandemic in the region. My last afternoon there, South African scientists announced the discovery of the Omicron variant. Hours later, I got on a plane in Johannesburg to head home to Canada.

By the time I landed for my connection in Amsterdam on the morning of Nov. 26, the world had gone into full panic mode and I was swept up in a chaotic, at times frightening, tangle of orders and conflicting rules that seemed driven more by fear than medical science.

My firsthand journey through Covid response measures has shown me that, two years into this, we have yet to learn how to anticipate how both viruses and people will behave, or how to plan accordingly. We are going to need to get much better at both if we are to get through the next pandemic with less loss of life and less suffering.

When my plane touched down, a flight attendant informed us that passengers would need to be tested for the coronavirus before we could continue our journeys. Five hours later, we were still on the tarmac, the plane sealed up tight, with more and more travelers shedding their masks. The pilot said he could not procure food and drink for us because the airport authorities “would not permit” catering trucks to approach the plane.

We were eventually bused into an unused departure area and given virus tests. Hours ticked by in the stuffy room. Many gave up even a pretense of masking. The authorities made no attempt to stop them. I learned from a Dutch colleague that the health ministry had reported that 15 people had tested positive out of 110 on my flight and a second plane from Cape Town that arrived at the same time — an infection rate of 14 percent.

I looked around the room full of people, many shouting men and wailing toddlers, and began quietly to panic. Finally at 3 a.m., a couple of weary-looking public health staff members packed us into a line, had us hold up our passports, one by one, and read the results from a database. My test was negative, and I signed a document in Dutch promising that I had somewhere to quarantine at home, and that I would leave the country to go there.

That pledge seemed like a bad idea for public health, but I’d been awake for 42 hours, so I signed and handed it over. I spent another nine hours in an increasingly frantic search for someone who could help me gain access to a copy of my putative negative test. Finally, at the 11th hour, I got the test results and flew to Toronto.

There, I identified myself to a border agent as having flown from Johannesburg, and he waved me into a special line. A public health screener took my name, address and temperature — then sent me on my way.

“I was just held in detention for almost a day with people we know have Omicron,” I said, almost pleading. “You want to quarantine me!”

She shrugged. “I think you should go get your connection, and maybe quarantine yourself at home. Get tested on Day 4. I have no other guidelines for you.” This was the first of what would be days of conflicting, confusing messages from health authorities that left me struggling to figure out how best to keep people safe.