Omicron is already changing how medicine fights COVID-19.

Although it only became widespread across the United States in the past week, doctors, pharmacists and drug companies said they need different tools against the new variant.

Two well-used monoclonal antibodies are unlikely to be effective against omicron. In their place, the government accelerated authorization of two antivirals that can be taken right after diagnosis to prevent illnesses from becoming severe.

The Food and Drug Administration on Wednesday authorized use of Pfizer's Paxlovid, a series of pills, taken at home that prevent nearly 90% of severe COVID-19 among those at high risk. On Thursday, the FDA authorized use of a second antiviral, molnupiravir, which appears to prevent progression to severe disease about 30% of the time.

"As we face omicron, the nation's medicine cabinet of treatments gives us more options to protect the American people," said Jeff Zients, the White House Coronavirus Response Coordinator. "We have tools to keep people safe and we will continue to use them."