U.K. Health Secretary Sajid Javid confirmed that two people have tested positive with the omicron variant in the southeastern English town of Chelmsford and in the central city of Nottingham.

He said the cases were linked and related to travel from southern Africa.

Javid said the two confirmed cases are self-isolating alongside their households while contact tracing and targeted testing takes place.

He also said arrivals from Angola, Malawi, Mozambique and Zambia will have to quarantine from Sunday and stressed the importance of booster jabs.

Many countries have slapped restrictions on various African countries over the past couple of days including Australia, Brazil, Canada, the European Union, Iran, Japan, Thailand and the United States, in response to warnings over the transmissibility of the new variant — against the advice of the World Health Organization.

Pharmaceutical companies expressed optimism that they could finesse their vaccines to deal with the new variant though that would clearly take some time.

Despite the banning of flights, there are mounting concerns that the variant has already been widely seeded around the world.

In addition to the U.K, cases have been reported in travelers in Belgium, Israel and Hong Kong. Germany also said it suspected a positive case and Dutch authorities were testing whether 61 people who arrived on two flights from South Africa with COVID-19 have the omicron variant.

The planes arrived in the Netherlands from Johannesburg and Cape Town shortly after the Dutch government imposed a ban on flights from southern African nations.

The 539 travelers who tested negative were allowed to return home or continue their journeys to other countries. Under government regulations, those who live in the Netherlands and are allowed to return home must self-isolate for at least five days.

Meanwhile, a German official said that there’s a “very high probability” that the omicron variant has already arrived in the country.

The global health body has named the new variant omicron, labeling it a variant of concern because of its high number of mutations and some early evidence that it carries a higher degree of infection than other variants.

That means people who contracted COVID-19 and recovered could be subject to catching it again. It could take weeks to know if current vaccines are less effective against it.

Nearly two years on since the start of the pandemic that has claimed more than 5 million lives around the world, countries are on high alert.

A number of pharmaceutical firms, including AstraZeneca, Moderna, Novavax and Pfizer, said they have plans in place to adapt their vaccines in light of the emergence of omicron. Pfizer and its partner BioNTech said they expect to be able to tweak their vaccine in around 100 days. — Agencies