As omicron variant is detected around the world, travel bans may be too late, experts say

“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,” she added.

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 Africa appear to involve people who had traveled to the continent.

Two planes carrying some 600 passengers from South Africa landed in the Netherlands with 61 people infected with the coronavirus — including some cases believed to be the new omicron variant — Dutch health authorities said Saturday.

Health officials in Australia on Sunday confirmed two fully vaccinated, asymptomatic passengers on a flight into Sydney tested positive for the new coronavirus variant and are now in government isolation. They were among 14 people from southern Africa who arrived Saturday evening on a flight from Doha, Qatar, officials said. All 260 people aboard the plane are considered close contacts and have been ordered to self-quarantine. Canberra announced a two-week travel ban on nine southern African countries.

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

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

In Britain, the former head of the government’s vaccine task force accused leaders of ignoring a plan to prepare for the emergence of vaccine-resistant variants. Clive Dix, who chaired the vaccine task force until April, told the Guardian’s Observer that he wrote a “very specific proposal on what we should put in place right now for the emergence of any new virus that escaped the vaccine,” adding: “I haven’t seen a sign of any of those activities yet.”

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 lockdowns used to control the virus in the early days of the pandemic.

Singapore, which has been easing border restrictions, is watching the new omicron variant “very closely” and may be forced to roll back some easing measures, Prime Minister Lee Hsien Loong said in a speech Sunday, Bloomberg reported.

White House officials said that the world’s failure to contain the rapid spread of delta this spring demonstrated the need to be vigilant in staving off omicron, which public health experts fear could sicken vaccinated people and spread more rapidly than delta.

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

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

President Biden and White House officials this weekend also urged unvaccinated Americans to get inoculated and called on eligible adults to get booster shots, saying that the vaccines remain the best protection against the virus.

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

“Every time the virus reproduces inside someone, there’s a chance of it mutating and a new variant emerging,” said Vinod Balasubramaniam, a virologist at Monash University in Malaysia. “The main way to stop variants is equal global vaccination. The emergence of omicron reminds us of how important that goal remains.”

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 strain of the virus 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 the 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.

Joel Achenbach, Chico Harlan and Lesley Wroughton contributed to this article.