COVID data tracker weekly review : interpretative summary for January 6, 2023
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Up-to-date Information

Up-to-Date Info: To find the latest CDC information on this topic go to:

COVID data tracker weekly review : interpretative summary for January 6, 2023

Filetype[PDF-2.80 MB]

  • English

  • Details:

    • Alternative Title:
      New Year, Same Variant
    • Description:
      New Year, Same Variant

      DC’s goal is to provide actionable information to public health professionals and the American public. Because Omicron sublineage XBB.1.5 data were displayed separately from XBB data on COVID Data Tracker’s Nowcast projections for the first time last week, we thought it would be helpful to explain the different variant proportion information CDC provides. This includes how the Nowcast forecasting tool works—what it is (a projection based on a model that has been accurate over time) versus what it isn’t (a literal, real-time count of variants based on sequenced viruses from people with COVID-19).

      CDC uses two methods to display variant proportions: weighted estimates and Nowcast estimates. Weighted estimates for each circulating lineage are very precise, but it takes two to three weeks for sample collection, specimen treatment, shipping, and analysis to occur. CDC uses Nowcast to forecast variant proportions before the weighted estimates are available.

      Sublineages with weighted estimates less than 1% of all circulating variants are combined with their parent lineage for reporting of both weighted and Nowcast estimates. Variant proportion estimates for XBB.1.5 were first separated from its parent (XBB) the week of December 31, when its most recent weighted estimate (based on information from the week of December 10) rose to about 4%. Because of its fast growth rate, its Nowcast estimate was projected to be around 41% by the end of December.

      But projections can be uncertain when a variant is just beginning to spread. When Nowcast predicted XBB.1.5 at 41%, there was a wide prediction range of about 23% to 61%. Since then, more data have come in from mid-December, as well as additional data delayed by the holidays. As a result, the projection for the week ending December 31 was revised to 18%, but with a higher degree of certainty (prediction range of 9% to 33%), followed by an increase to 28% for the most recent week of January 6 (prediction range of 14% to 47%).

      These findings demonstrate that XBB.1.5 is spreading quickly. At this time, CDC’s COVID-19 guidance remains the same about how people can best protect themselves from serious illness. CDC will continue to investigate the ways in which XBB.1.5 may be different from other Omicron lineages and will continue to update COVID Data Tracker’s Variant Proportions page on a weekly basis.

    • Content Notes:
      It’s time to pick out your costume and get ready to celebrate Halloween! Over the past two-plus years, we’ve learned new ways to enjoy pandemic holidays, and “outside is always safer” has been the mantra for these holiday gatherings. Luckily, that’s easy to do on Halloween, because trick-or-treating generally involves plenty of outdoor time. But that doesn’t mean it’s totally risk-free. Here are some more tips for staying COVID-safe this Halloween.

      • Stay home if you’re sick. Skip the Halloween party if you aren’t feeling well.

      • Get tested if you have COVID-19 symptoms.

      • Take precautions in crowded or indoor events as informed by your county’s COVID-19 Community Level, like wearing a high-quality mask (and Halloween masks don’t count). Consider making the mask part of the costume—like a doctor, nurse, ninja, or cowboy.

      • If you’re hosting celebrations, review options for improving ventilation in your home. This can help you reduce virus particles in your home and keep COVID-19 from spreading.

      • Keep your hands clean. If you’re out trick-or-treating, bring hand sanitizer. If you’re giving out candy, wash your hands frequently.

      And of course, the best way to protect yourself and others from severe illness from COVID-19 on Halloween (and every day) is to stay up to date on your COVID-19 vaccinations! Use this tool to find out when you can get a booster.

      Note to Readers: On October 12, 2022, CDC recommended updated (bivalent) COVID-19 boosters for children ages 5 years and older in the United States, making the updated boosters available to millions of children in this age group.

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