LONDON – As the still mysterious variant of Omicron hit American shores, the World Health Organization scolded rich countries for travel bans on Wednesday and fired those who poured resources into vaccine-booster campaigns when billions in poor countries were still getting their first vaccinations had received.

Comments from WHO officials re-raise problematic questions of equity in the world’s handling of the coronavirus pandemic, since a large gap emerged between rich and poor countries over vaccine availability earlier this year.

But amid fears of a new wave of Covid-19 that seemed unlikely to sway leaders in Europe, Asia and the United States, who reported their first confirmed Omicron case in California on Wednesday. They are trying to protect their populations from the variant – much is still unknown about it – by increasing their protection and tightening restrictions on inbound travel.

Travelers responded with confusion and dismay at the news that the United States intends to tighten testing requirements and screening of arriving passengers. That decision came after Japan, Israel and Morocco blocked foreign travelers and Australia delayed reopening its borders by two weeks.

“It’s a shame because travel has just reopened,” said Giritharan Sripathy, a Singaporean film producer scheduled to fly from London to New York on Thursday. Mr Sripathy, who had already done a PCR test three days before his flight as required, said he had scheduled a new rapid test as a precaution “in case they change the rules tomorrow”.

WHO added its voice to the objections, calling travel restrictions against South African countries ineffective and unfair.

“Blanket travel bans will not prevent the spread of Omicron and will put a heavy burden on lives and livelihoods,” said WHO Director General Tedros Adhanom Ghebreyesus at a press conference in Geneva.

He praised Botswana and South Africa, where the earliest cases of Omicron were discovered last month, for promptly reporting the results to international health officials. “I am deeply concerned that these countries are now being punished by others for doing the right thing,” he said.

Other WHO officials said the United States and European countries’ bans on South African countries would hamper efforts to control the variant because biological samples could not be shipped from those countries even though they would be willing to share them. The Omicron variant was discovered in two dozen countries by Wednesday – just six days after it first existed revealed to the world – and Dr. Tedros warned that the number would increase.

The WHO has also expressed skepticism about ambitious booster plans allegedly at the expense of primary vaccination in less affluent countries. The UK announced a massive new campaign this week to provide booster injections to all adults by the end of January. Other European countries and the Biden government are also pushing for these shots as a first line of defense against the variant to give scientists time to decipher its genomic code.

However, WHO officials said there was still no evidence that boosters prevented disease and hospitalization in people infected with variants. They suggested that the vaccines stored by the UK and other countries could be better used in places where much of the population had not yet been vaccinated.

“It’s a luxurious position when you have enough vaccine for it,” said Michael Ryan, executive director of the WHO’s emergency health program, referring to the UK campaign.

Injustices came back into the spotlight as WHO member states took the first step towards a legally binding treaty to strengthen global defenses against pandemics that many governments are hoping for.

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Dec. 02/02/2021, 12:30 p.m. ET

WHO will set up a negotiating body to begin drafting an international agreement that will ensure a more coherent and equitable response to future outbreaks. But the United States and other countries have pushed for a weaker mechanism that does not impose any legal obligations on member states.

The patchwork of travel restrictions imposed after the advent of Omicron has shown once again that countries are now determined to act swiftly and unilaterally to protect their people, regardless of how that might affect their neighbors or whether the measures will achieve their stated goal.

However, public health experts were skeptical that the restrictions would prove effective.

“Travel restrictions can delay, but not stop, imports and widespread sowing,” said Devi Sridhar, director of the University of Edinburgh’s global health program. “The variant will be found almost everywhere in the next few days, I’m sure of that.”

The most important unanswered question is the transmission rate and whether Omicron could overtake the Delta variant in order to establish itself as the dominant strain of the virus.

Professor Sridhar and other experts have called for greater global coordination, and WHO’s efforts towards an international treaty are a step in that direction. Yet the United States, with the support of Brazil and other countries, refused to make any legally binding commitments and kept open the possibility of a weaker agreement.

Proponents want to commit to sharing data, virus samples and technology, and ensuring equitable distribution of vaccines. But that raises politically sensitive issues of national sovereignty over access to the outbreak sites and investigation into the causes of disease. China, for example, opposed calls for an independent investigation into the occurrence of the coronavirus in the city of Wuhan in late 2019.

United Nations Secretary-General António Guterres, who has called the hoarding of vaccines by wealthy nations “profanity,” reiterated criticism of the international response to fear of Omicron.

“The people of Africa cannot be held responsible for the immorally low levels of vaccinations available,” he told reporters after meeting with the chairman of the African Union Commission, Moussa Faki Mahamat from Chad. “Nor should they be collectively punished for identifying important scientific and health information and sharing it with the world.”

The Coronavirus Pandemic: Important Things You Should Know

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Travel restrictions and bans. With Omicron cases increasing around the world, countries respond in different ways. Japan joined Israel and Morocco in blocking all foreign travelers, and Australia delayed reopening its borders by two weeks. The CDC plans to increase testing and screening of international passengers to the USA

A patchwork of regulations. As the new Omicron variant spread all over the world, two KLM flights from South Africa became symbols of the scatter shot and looseness Global Approach to Coronavirus Containment. Of the more than 60 people who tested positive for the virus, at least 14 had omicrons.

A new way of treatment. A panel of experts voted to recommend that the FDA: a Covid pill from Merck for high risk adults, the first in a new class of antiviral drugs that could work against a variety of flavors, including Omicron. The pill could be approved within a few days and will be available until the end of the year.

Compulsory vaccination in Africa. The evidence of the Omicron variant in Africa signals the next stage in the fight against Covid-19: vaccinating more people in poorer countries. But although vaccine supplies are becoming adequate, the new hurdle is overcome local skepticism or open hostility.

The limitless nature of the virus, Guterres said, means that “travel restrictions that isolate a single country or region are not only deeply unfair and punitive – they are ineffective.”

While the United States does not weigh up Japan’s blanket travel ban on foreign visitors, the restrictions weighed up by the Centers for Disease Control and Prevention in the United States are of widespread concern. The agency is considering requiring travelers to submit a negative result of a test within 24 hours of departure, a spokesman said on Tuesday night.

Although the CDC hasn’t officially announced the changes, the prospect sent travelers looking for updates, booked preventive tests where they could, and scoured airline websites for reservation changes as the pandemic threatened to change another travel season in December .

Carlos Valencia, a dual Spanish-American citizen whose Seville-based company is studying abroad for American students, had planned to return to the United States in January. But he said he would put the trip on hold until “at least it is clear whether the new rules make a trip feasible”.

Whatever the restrictions, they were “much exaggerated – especially when you consider how lax the US has been in getting people to wear face masks and their own health precautions.”

Emanuela Giorgetti, a teacher in northern Italy, had hoped to come to Chicago for Christmas with her fiancé, whom she hadn’t seen for almost two years. “When I heard the message,” she said, “I thought, ‘Here we go again.'”

Given the potential threat posed by Omicron, she said she understood the impetus to tighten the rules. But it still seemed unfair.

“We have more people vaccinated in Italy than in the US, we wear masks indoors and try to follow the rules,” said Giorgetti.

Coverage was contributed by Nick Cumming-Bruce, Rick Gladstone, Raphael Minder, Gaia Pianigiani, Michael D. Shear, and John Yoon.