President Biden will remove the ban on travel between the United States and countries in southern Africa at midnight on Dec. 31, a senior administration official said on Friday, reversing restrictions imposed last month to combat the spread of the Omicron variant.

The region’s leaders had denounced the ban as unfair, discriminatory and unnecessary.

Mr. Biden made the decision this week on the advice of his medical team based on findings that existing Covid vaccines are effective against severe disease with the highly contagious Omicron variant, especially among people who have received a booster shot of the Pfizer-BioNTech or Moderna vaccine, the senior official said in an email.

The decision followed the British government’s announcement on Tuesday that it was lifting its restrictions on travelers arriving from 11 African countries.

Officials with the Centers for Disease Control and Prevention also advised Mr. Biden and his team that Omicron, which has passed Delta as the dominant variant in the United States, was so widely present across the world that it no longer made sense to restrict travel to and from South Africa, Botswana, Eswatini, Lesotho, Malawi, Mozambique and Namibia, the official said.

The ban was announced on Nov. 26, after officials in South Africa reported the emergence of the variant, which has a large number of mutations that allow it to evade the immune response of even vaccinated people. The ban went into effect at midnight on Nov. 29.

The countries in southern Africa will now be subject to the same protocols imposed on all nations, with a requirement that foreign incoming travelers be fully vaccinated and show proof of a negative coronavirus test within one day of their trips.

“We certainly welcome this development,” Clayson Monyela, head of public diplomacy in South Africa’s department of international relations, said on Friday. “We’ve always maintained that these travel bans were unscientific and discriminatory. They’ve had a devastating impact on our travel and tourism industry, on business and families.”

Lemogang Kwape, Botswana’s foreign minister, said officials there were delighted by the news. “We hope the world would come together as one to fight all the challenges that we are besieged with,” he added.

The restrictions drew immediate criticism from regional leaders, critics from Mr. Biden’s own party and international health officials.

“Travel restrictions may play a role in slightly reducing the spread of Covid-19 but place a heavy burden on lives and livelihoods,” Matshidiso Moeti, the regional director for Africa for the World Health Organization, said at the time the ban was announced. “If restrictions are implemented, they should not be unnecessarily invasive or intrusive, and should be scientifically based.”