Despite shutting its borders to travel from high-risk southern African countries, Australia became the latest country to report community transmission of the new variant, a day after it was found locally in five US states.

Omicron started gaining a foothold in Asia this week, with cases reported in India, Japan, Malaysia, Singapore and South Korea. Many governments have tightened travel rules to keep the new variant out, but the WHO’s warning to the Asia-Pacific, a region of about 650 million people, stressed that border controls could only buy them time.

“People should not only rely on border measures,” Takeshi Kasai, WHO regional director for the western Pacific, told a virtual media briefing. “What is most important is to prepare for these variants with potential high transmissibility. So far the information available suggests we don’t have to change our approach.”

Vaccination rates vary from country to country in the Asia-Pacific but there are worrying gaps. Indonesia, the world’s fourth most populous country and once Asia’s COVID-19 epicentre, has fully inoculated only about 35 per cent of its population of 270 million people.

Australia’s chief medical officer said Omicron was likely to become the dominant variant globally within months, but at this stage there was no evidence it was any more dangerous than Delta which swept the world earlier this year. “I suspect within the (next few) months, Omicron will be the new virus in the world,” Paul Kelly, the top medical advisor to the Australian government, told reporters.

In the US, the Biden administration unveiled a suite of measures to guard against the virus spreading. International air travellers arriving in the US will have to obtain a negative COVID-19 test within one day of travel. Less than 60 per cent of the US population, or 196 million people, have been fully vaccinated, one of the lowest rates among wealthy nations.

Global travel curbs have accelerated with Hong Kong, the Netherlands, Norway and Russia, among others, announcing fresh measures on Thursday. Malaysia said on Friday that it would tighten restrictions further.

Aside from wreaking havoc in the travel industry, the clampdown has pounded financial markets and undermined major economies just as they were beginning to recover from the lockdowns triggered by Delta. Shares in India, Japan, and South Korea fell on Friday after overnight losses on Wall Street.

Europe’s biggest economy, Germany, said it would bar the unvaccinated from all but essential businesses, and legislation to make vaccination mandatory would be drafted for early next year.

Several countries including Britain and the United States were bringing forward plans to offer booster shots, but, like travel bans, this is controversial. Australian authorities said on Friday there was “no evidence” such moves would be effective.