The Biden administration is focusing on booster shots as a key weapon in efforts to protect the nation against a potentially dangerous coronavirus variant even as the extent of the threat remains unclear, the White House said Sunday.

A group of senior health officials had a call with South African scientists Sunday to review the latest on the new variant and to help inform next steps, according to two senior administration officials who spoke on the condition of anonymity to describe internal discussions.

In an update Sunday, the World Health Organization (WHO) said it is still too early to know whether the new variant, dubbed omicron, is more transmissible than the delta variant. There remains little understanding about the severity of illness caused by the variant and the rate of hospitalization. Scientists in South Africa, where the variant was first identified, said they expect more breakthrough cases in people vaccinated against the coronavirus.

Researchers could soon have a better indication of how well vaccines protect against the new variant. But the Biden administration is already moving to urge as many Americans as possible to receive booster shots in coming days as the best means to protect against omicron.

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That campaign is likely to involve messages urging people to get boosters and efforts to make sure the shots are available in as many locations as possible.


“The vaccinated people, the thing that we know for sure is that when you boost someone who’s been vaccinated with two doses of Pfizer or Moderna, you increase the level of neutralizing antibodies extraordinarily high – many fold higher than even the peak following the first two doses,” Anthony Fauci, President Joe Biden’s chief medical adviser, said in an interview with The Washington Post.

Fauci said “it is quite conceivable if not likely” that booster shots will provide at least a partial shield of protection against the new variant.

Omicron has a high number of mutations that could make it more easily transmissible, though that remains unclear. In South Africa, cases are rising but it is not yet clear whether the rise is fueled by omicron or other factors, according to the WHO.

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Biden on Sunday met with Fauci and members of the White House covid-19 response team. Fauci told Biden it would take about two more weeks before there was more information on the transmissibility, severity and other characteristics of the variant, but stressed that he believed vaccines would continue to provide a degree of protection, according to a White House account of the meeting.

The White House said the covid response team’s recommendation was for all adults to receive a booster as soon as possible and for unvaccinated adults and eligible children to get immunized. People 18 and older are eligible for booster shots.


Experts, including Fauci, have said it is highly unlikely that the vaccines offer no protection against the new variant. The WHO said it was working with “a large number of researchers around the world” to understand the impact omicron would have on existing vaccines and antivirals. Even if there is diminished protection compared with other variants, there is a benefit to increasing the number of virus-neutralizing antibodies by getting a booster shot, senior health officials and experts said.

“If you’re worried about omicron, do the same things as if you’re worried about delta. Get your boost and get fully vaccinated,” said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine.

The Centers for Disease Control and Prevention increased communication with state public health officials in recent days as federal disease trackers learned more from South African counterparts, according to a U.S. Health and Human Services official. That has included daily calls with state-level officials, including epidemiologists, lab directors and city and county authorities.

The White House is also organizing meetings with state health officials, members of Congress and governors during the coming days, a White House official said.

Omicron has not yet been confirmed in the United States, but Biden officials said the country’s genomic surveillance system is sequencing nearly 80,000 samples a week and that they are confident it can quickly identify the variant if it is in the United States.

While experts said boosters could be helpful in protecting against the omicron variant, some cautioned against using the additional shots at the expense of providing doses to countries where vaccination rates remain low.


Celine Gounder, an epidemiologist and infectious-diseases specialist who advised the Biden administration’s transition team on the covid-19 response, said boosters should be part of the response to the omicron variant if it is “truly immune-evading” because the additional shots significantly boost antibody levels.

But Gounder said a booster-heavy approach could mean much of the developing world remains unvaccinated, creating conditions for other variants to emerge.

“You have one approach that has a likely short-term benefit versus another approach that has a very likely long-term benefit, and how do you weigh one versus the other?” Gounder said.

But Fauci and others said millions of vaccine doses shipped to lower-income nations have gone unused, demonstrating the complexity of the global challenge. South African officials recently asked vaccine manufacturers to slow shipments so the country could maximize its existing stock.

U.S. officials asked South African officials over the weekend whether they needed more doses but were told vaccine uptake, and not supply, was the issue, a senior administration official said.

There was more blowback on the international front for the United States and European countries after nations closed their borders to travelers from southern Africa. They also faced words of caution from experts that the travel bans may be too late, with confirmed and suspected cases emerging as far away as Asia and Australia.


“By the time we have enough information to institute a travel ban, the cat’s already out of the bag, so to speak,” Nicole A. Errett, a professor at the University of Washington who has done research on public health emergency preparedness, said in an email. “Omicron has already been detected in other continents. A travel ban could in theory buy some time by reducing the spread of new seed cases, but we are talking on the order of days to weeks.”

Confirmed and suspected covid-19 cases caused by the new variant have been detected in a growing number of regions, including Britain, Belgium, Botswana, Germany, Italy, Hong Kong, Israel and the Czech Republic. Most of the cases outside of Africa appear to involve people who had traveled to the continent.

Austria also joined the growing list of countries where the variant has been reported, detecting its first suspected case in the Tirol region, Reuters reported Sunday, citing Austrian officials.

Two planes carrying about 600 passengers from South Africa landed Saturday in the Netherlands with 61 people infected with the coronavirus – including 13 cases of the new omicron variant – Dutch health authorities said Sunday.

Health officials in Australia on Sunday confirmed two fully vaccinated, asymptomatic passengers on a flight into Sydney tested positive for the new variant and are in government isolation.

“This clearly demonstrates the pandemic is not over,” Dominic Perrottet, the premier of New South Wales state, home to Sydney, told reporters Sunday. “There are limits to what the state and federal government can do: These variants will get into the country. It is inevitable.”


The appearance of a new and potentially more menacing variant raises questions about what lessons officials have learned in the two years since the novel coronavirus emerged, and whether they’re prepared for worrisome mutations that could evade vaccines.

On Sunday, Britain’s health secretary, Sajid Javid, said vaccines may be less effective against omicron, acknowledging “we just don’t know enough” about the new variant to understand the risk.

Starting Tuesday, face masks will be compulsory in shops and on public transport in England. The United Kingdom will also require all international travelers to take a PCR test, which can detect the new variant, and to self-quarantine until results are returned.

Europe is in the grips of an increasingly deadly outbreak of the fast-spreading delta variant that has prompted officials in some countries to revert to measures such as shutdowns used to control the virus in the early days of the pandemic.

White House officials said the world’s failure to contain the rapid spread of the delta variant this spring demonstrated the need to be vigilant in staving off omicron.

In designating omicron a “variant of concern,” the WHO said Friday that preliminary evidence suggests an increased risk of reinfection with the variant for people who have previously had the virus, compared with other variants. However, there are high rates of people living with HIV and AIDS in southern Africa, which experts said makes it harder to interpret the effectiveness of vaccine-induced or natural immunity against infection.


Only about 24% of South Africans are fully vaccinated, according to Johns Hopkins University data, compared with nearly 60% of Americans.

U.S. officials said they jumped into action after learning that the new variant contained long-feared mutations and appeared to descend from a different genetic lineage than delta. Senior officials such as Fauci, CDC Director Rochelle Walensky and others began discussions with government scientists, South African officials and vaccine manufacturers that intensified on Thanksgiving Day.

The world’s major manufacturers of coronavirus vaccines, including Pfizer and BioNTech, Johnson & Johnson, Moderna and Chinese vaccine maker Sinovac, said they are working to investigate the new variant and adapt their shots if needed.

Experts cautioned that the flurry of activity to fight omicron may turn out to be largely unnecessary, as researchers learn in coming days whether current vaccines can ward off the variant or successfully limit symptoms.

“Not all covid-19 variants cause trouble. For example, lambda and mu have not taken off globally. So it is possible that the new variant, omicron, could hopefully fizzle out,” said Sanjaya Senanayake, an infectious-diseases expert at the Australian National University.

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The Washington Post’s Joel Achenbach, Dan Diamond, Chico Harlan, Jennifer Hassan, María Luisa Paúl and Lesley Wroughton contributed to this report.