US President Joe Biden met in person with Fauci and members of the White House COVID Response Team on Sunday.
"Dr. Fauci informed the President that while it will take approximately two more weeks to have more definitive information on the transmissibility, severity, and other characteristics of the variant, he continues to believe that existing vaccines are likely to provide a degree of protection against severe cases of COVID," the White House said in a statement.
The chief medical expert emphasized that boosters for fully vaccinated individuals provide the strongest available protection from the coronavirus.
"The COVID Response Team’s immediate recommendation to all vaccinated adults is to get a booster shot as soon as possible ...those adults and children who are not yet fully vaccinated should get vaccinated immediately," the White House said.
Biden is expected to provide more updates on Omicron on Monday, according to the US government.
On Saturday, Fauci warned that the Omicron variant was likely to spread all over the United States.
The first two cases of the Omicron coronavirus strain were confirmed in Canada on Sunday.
The World Health Organization (WHO) said on Sunday that there is not enough data yet to state that the new strain is more dangerous than Delta, and existing vaccines remain effective.
On Friday, the WHO identified the new South African strain, Omicron, as one of concern, since it may be more transmissible and dangerous. Cases of the new variant have already been confirmed in multiple countries and governments rushed to suspend travel with southern African nations in order to prevent the spread of the new strain.