JOHANNESBURG — Previous infection with the coronavirus may offer less protection against the new variant first identified in South Africa, scientists said on Monday, although they hope that vaccines will still work.

Studies also found that the new variant binds more strongly and readily to human cells. That helps explain why it seems to be spreading around 50% quicker than previous versions, leading South African epidemiologist Salim Abdool Karim said.

The 501Y.V2 variant was identified by South African genomics experts late last year. It has been the main driver of a second wave of national coronavirus disease 2019 (COVID-19) infections, which hit a new daily peak above 21,000 cases earlier this month.

It is one of several new variants found in recent months, including others first discovered in England and Brazil, which scientists worry are hastening the spread of COVID-19.

“Convalescent serum studies suggest natural antibodies are less effective,” Mr. Abdool Karim said, introducing the research, “(but) current data suggest the new variant is not more severe.”

British scientists and politicians have expressed concern that vaccines currently being deployed or in development could be less effective against the variant.

Scientists speaking at the virtual panel on Monday said there was not yet a clear answer to that question and that studies were continuing.

“We have reason to be concerned because the virus has found a way to escape from previous antibodies,” Alex Sigal, a virologist at the Africa Health Research Institute, said.

“The world has underestimated this virus. This virus can evolve, it … is adapting to us.”

Earlier, South African researchers said that since vaccines induce a broad immune response it was unlikely that the mutations in the spike protein of the variant would completely negate their effect.

The researchers reiterated that notion on Monday.

“Our immune systems are extraordinarily clever,” Willem Hanekom, one of the team, said. “There may be compensation through other arms of the immune system that allow vaccines to still work.” The 501Y.V2 variant has spread to nations in Europe, Asia and the Americas, as well as several other African countries, causing some states to impose restrictions on travel to and from South Africa. — Reuters

WASHINGTON — US President-elect Joe Biden plans to quickly extend travel restrictions barring travel by most people who have recently been in much of Europe and Brazil soon after President Donald Trump lifted those requirements effective Jan. 26, a spokeswoman for Mr. Biden said.

Mr. Trump signed an order Monday lifting the restrictions he imposed early last year in response to the pandemic — a decision first reported Monday by Reuters — after winning support from coronavirus task force members and public health officials.

Soon after Mr. Trump’s order was made public, Biden spokeswoman Jen Psaki tweeted “on the advice of our medical team, the Administration does not intend to lift these restrictions on 1/26.”

She added that “With the pandemic worsening, and more contagious variants emerging around the world, this is not the time to be lifting restrictions on international travel.”

Until Mr. Biden acts, Mr. Trump’s order ends restrictions the same day that new coronavirus disease 2019 (COVID-19) test requirements take effect for all international visitors. Mr. Trump is due to leave office on Wednesday.

Last week, the head of the Centers for Disease Control (CDC) and Prevention signed an order requiring nearly all air travelers to present a negative coronavirus test or proof of recovery from COVID-19 to enter the United States starting on Jan. 26.

The restrictions Trump rescinded have barred nearly all non-US citizens who within the last 14 days have been in Brazil, the United Kingdom, Ireland and the 26 countries of the Schengen area in Europe that allow travel across open borders.

The US restrictions barring most visitors from Europe have been in place since mid-March when Trump signed proclamations imposing them, while the Brazilian entry ban was imposed in May. Ms. Psaki added that “in fact, we plan to strengthen public health measures around international travel in order to further mitigate the spread of COVID-19.” The Biden transition did not immediately respond to a request to comment on if it planned to expand the countries covered.

Mr. Biden, once in office, has the legal authority to reimpose the restrictions.

Last Tuesday, Marty Cetron, director of CDC’s global migration and quarantine division, told Reuters those entry bans were an “opening act strategy” to address the virus spread and should now be “actively reconsidered.”

Airlines had hoped the new testing requirements would clear the way for the administration to lift the restrictions that reduced travel from some European countries by 95% or more.

They had pressed senior White House officials about the issue in recent days.

Many administration officials for months argued the restrictions no longer made sense given most countries were not subject to the entry bans. Others have argued the United States should not drop entry bans since many European countries still block most US citizens.

Reuters previously reported the White House was not considering lifting entry bans on most non-US citizens who have recently been in China or Iran. Mr. Trump confirmed Monday he would not lift those. — Reuters