Omicron updates: Possible peaks, viral loads, vaccines

Has Omicron peaked in NYC? It sure seems like it, according to city data; screenshot retrieved from NYC Health dashboard on January 16.

These update posts are getting shorter as time goes on, but we’re still learning about this variant! A few news items from this week:

  • Omicron is now causing almost 100% of new COVID-19 cases in the U.S. In the CDC’s latest variant proportions update, the agency estimated that 98% of new COVID-19 cases were caused by Omicron in the week ending January 8. The CDC also revised estimates for previous weeks, though the revisions were not as significant as they have been in the past—suggesting that the numbers are now fairly close to accurate, but will continue to be tweaked as more sequencing data come in.
  • Major Northeast hotspots appear to be peaking. Last week, I wrote that New York City’s Omicron wave seemed to have reached its peak. The trend has continued into this week: the new case rate and test positivity rate have both fallen consistently since peaking on January 3. Similarly, in Boston, the Omicron levels detected in the city’s wastewater have declined steeply since early January. The daily case rate is also going down in Washington, D.C., and in the Northeast region overall. Still, hospitals are still overwhelmed throughout the region, and it’s unlikely that cases will go down as quickly or as decisively as they went up.

  • New NYC report provides data on the city’s Omicron wave. Speaking of NYC: the city’s public health department recently put out a new report detailing the variant’s impact. The variant “has accounted for nearly all coronavirus samples sequenced in NYC” since Christmas, the report’s authors write. Also, while a smaller share of Omicron cases led to hospitalization compared to the Delta wave, more people have been hospitalized overall because of sheer case numbers. Unvaccinated New Yorkers, Black New Yorkers, and those over age 75 have been most likely to require hospitalization.
  • Real-world study suggests rapid at-home tests work well at detecting Omicron. A new study from the University of California, San Francisco, released this week as a preprint, analyzed rapid antigen tests’ capacity to detect Omicron by comparing rapid test results to PCR test results. The results: antigen tests correctly identified 95% of cases with high viral loads and 98% of symptomatic cases. In about one-third of the cases identified through PCR, patients tested negative on antigen tests; but this is in line with the tests’ accuracy for other variants.
  • Data from the NBA suggest Omicron’s viral load is pretty variable. Another new study posted as a preprint this week analyzed data from the National Basketball Association (NBA). The league’s regular testing policy allowed Harvard researchers to study viral loads in Omicron-positive patients, revealing that this variant had “lower peak viral load and more variable early viral growth durations than Delta,” according to one of the authors. In other words, some of the basketball players were highly contagious early into their Omicron infections, while others were less so; and the players had less virus in their bodies overall at the peak of their infections than in previous Delta infections. Also, a large number of the players were still contagious five days after they were diagnosed—which doesn’t bode well for the CDC’s new isolation guidance.
  • More confirmation that vaccinated people are protected from severe disease from Omicron. Another new study, this one published in Nature through the journal’s advance preview system for COVID-19 reports, confirms previous research about T cell response to Omicron. T cells are a key part of the immune system’s long-term memory apparatus; they help protect against severe symptoms and death. The study found that, in patients who were fully vaccinated (or, to a lesser degree, had a previous infection), T cells could recognize Omicron and protect people against its worst impacts.
  • Omicron adds urgency to the need to vaccinate the world—ideally, with mRNA vaccines. A report from advocacy groups PrEP4All and Partners In Health, written with scientists at Harvard, Columbia, and other institutions, found that 22 billion additional mRNA vaccine doses are needed to control the pandemic, now that Omicron has become the dominant variant in the world. The report specifies that mRNA vaccines are needed because other vaccine types are not capable of preventing Omicron infection, and likely are less effective against severe disease. “Future viral variants may become even more transmissible, immune evasive, and virulent than Delta or Omicron,” the report cautions.

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