Authorities at the airport in Amsterdam discovered 13 cases of the Omicron coronavirus variant in passengers on two flights arriving from South Africa on Friday. The New York Times adds:

Additional cases could emerge, as health officials were still examining test samples, said Hugo de Jonge, the country’s health minister, adding that the people who tested positive were in quarantine. The 61 passengers who had tested positive were among more than 500 who arrived on two separate flights.

Scientists caution that little is known about the variant but governments around the world have been moving quickly to halt flights from countries in southern Africa. It’s unknown if vaccines are effective against the variant but anecdotally, the Times reports:

In Australia, officials said that Omicron was detected in two travelers who flew into Sydney on Saturday evening on a Qatar Airways flight from Doha. They were asymptomatic and fully vaccinated, according to a statement from the health authority in New South Wales State. The travelers were placed into quarantine.

While the World Health Organization calls Omicron a “variant of concern,” more research is needed to determine the extent of the threat. As for those who are vaccinated, the Times writes:

William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health and other researchers said that vaccines will most likely protect against Omicron, but further studies are needed to determine how much of the shots’ effectiveness may be reduced.

Dr. Anthony Fauci echos the sentiment that more time is needed.

The BBC spoke to the South African doctor who found the new variant.