WASHINGTON (NEXSTAR) — While federal health officials say they are monitoring the spread of the omicron variant of coronavirus, they are reminding people that delta is still the main threat in the United States and that getting vaccinated is still the best way to slow the spread and protect yourself.

“Get vaccinated and get boosted,” Dr. Anthony Fauci, the chief medical advisor for the White House, advised.

The White House COVID-19 Response Team held a virtual briefing Friday, saying that omircron has now been identified in 40 countries and four U.S. states.

“We are equipped and prepared to fight the omicron variant head-on,” U.S. Centers for Disease Control and Prevention Director Rochelle Walensky said.

But she also emphasized that in the U.S., delta is still the biggest problem and it accounts for 99.9% of all domestic cases.

Research is underway to figure out exactly how contagious omicron is and how effective current vaccines are against it. Fauci said early indications are that vaccine boosters will protect people against omicron.

The White House is advancing rules to get ahead of the spread of omicron, expanding free at-home COVID-19 tests and continuing travel bans for eight southern African nations.

“I continue to rely on the scientists and asking them whether or not we have to move beyond what we did yesterday,” President Joe Biden said. “Right now, they’re saying no.”

House Minority Leader Kevin McCarthy, R-Calif., said he’s concerned that could change.

“President Biden’s only strategy so far has been to threaten Americans with more arbitrary COVID restrictions and mandates,” he said.

Next week, Senate Republicans will try to push back on the Biden administration’s pandemic strategies. They expect to hold a vote on a plan to reverse federal vaccine mandates they call unconstitutional.