CDC significantly cuts estimate of omicron’s prevalence in US

The Centers for Disease Control and Prevention (CDC) on Tuesday significantly revised downward the estimate of the percentage of new COVID-19 infections in the U.S. caused by the omicron variant of the virus.

According to agency data, omicron accounted for about 59 percent of all U.S. infections as of Dec. 25. Previously, the CDC said the omicron variant comprised 73 percent of all cases for the week ending Dec. 18. But that number has now been revised to 22.5 percent of all cases.

The omicron variant is highly transmissible and spreading rapidly, resulting in surges of infections even among people who are vaccinated. However, people who are vaccinated, and especially those who have received booster shots, are well protected against severe disease from the variant, experts say, meaning it poses the greatest risk to the unvaccinated.

The new estimates mean that while a majority of new infections are attributed to the omicron variant, the delta variant has not been sidelined, and still accounts for about 41 percent of infections. 

“Setting aside the question of how the initial estimate was so inaccurate, if CDC’s new estimate of Omicron prevalence is precise then it suggests that a good portion of the current hospitalizations we’re seeing from Covid may still be driven by Delta infections,” former Food and Drug Administration commissioner Scott Gottlieb tweeted on Tuesday. 

The omicron variant has some ability to evade the protection of vaccines, particularly in causing infection in people who have not been boosted. That means breakthrough infections are becoming more common. 

While evidence appears to show an omicron infection may be more mild for people who are fully vaccinated, experts say the experience is not likely to be pleasant, and people with such infections should expect to be sick for multiple days.

The U.S. is now averaging more than 206,000 new cases a day, according to the CDC, and that number is still climbing.