He said there were some breakthrough infections among those who recovered from the Delta variant and among those who were vaccinated.
But at the same time, he said, scientists do not know the severity of infections caused by the new variant. It is possible that it spreads faster but causes less severe illness.
“You don’t want to say you don’t want to worry, and you don’t want to say that you need to worry about the disease because we are gathering information quickly,” he said, adding: “Even though the numbers are still small, the doubling time pretty fast, and the steepness of the increase is really quite steep. “
Biden administration officials said they are continuing to work with health officials in other countries to find out more about this option.
“Travel restrictions will slow it down but not stop it,” said Dr. Ezekiel Emanuel, head of the University of Pennsylvania Department of Medical Ethics and adviser to the president during his transition. “The fact that he will come here is inevitable. The environment in which he appears may not be inevitable. We can change the environment. “
Mr Biden said Friday that the spread of the Omicron variant was another reason for vaccinated Americans to get boosters and unvaccinated Americans to get vaccinated – a view echoed by Dr Fauci. And Mr Biden said the development should push the international community to donate more vaccines to countries suffering from lack of access or low vaccination rates.
Michael Osterholm, an infectious disease expert at the University of Minnesota who also advised Mr Biden during his transition, said the administration did not have much choice about imposing a travel ban.
But Dr. Osterholm said it may be a while before scientists know if current vaccines are effective against this variant and how transmitted it is. One way to find out, he said, is through laboratory tests, which will take several weeks. Another way is to track the incidence of fractures in people who have already been vaccinated, which can take months.