Major news items for this week include the potential peak of the U.S.’s Omicron surge and real-world data from the CDC on how well booster shots work against this variant.
- Omicron is now causing nearly 100% of new COVID-19 cases in the U.S. The latest CDC estimates of variant prevalence put Omicron at 99.5% of new cases in the U.S. as of January 15, with Delta causing the remaining 0.5% of cases. I have to say, it’s incredibly striking not only how quickly Omicron outcompeted Delta (it went from 1% of new cases to nearly 100% in just six weeks), but also how both of these highly contagious variants have dominated the country so thoroughly that they’re now the only two variants present here at all. For comparison, Alpha only got to 70% of cases at its peak. These trends show how drastically both Delta and Omicron changed the trajectory of the pandemic.
- While the U.S. may be peaking, massive numbers of people are getting infected. As I noted in today’s National Numbers, America’s Omicron wave may have peaked this week, with the country’s massive case growth appearing to turn around. Computational biologist Trevor Bedford wrote a recent Twitter thread about this peak, pointing out that a huge share of the U.S. population was infected with Omicron in the past month: “between 18% and 23% of the country was infected by Omicron by Jan 17, with the large majority infected in a span of just ~4 weeks,” he hypothesized. By mid-February, Bedford says, this number could be “36%-46%.”
- The high infection numbers may give us “a bit of a break from the Covid roller coaster.” With so many people infected in such a short time, Omicron will have a huge impact on the “immunological landscape” of the U.S, Helen Branswell explains in a recent article for STAT News. Millions will have immunity from a recent infection, vaccination, or both; and Omicron’s unique biology may mean that people who caught this variant will be protected from other strains. As a result, the end of this wave may lead into “a bit of a break” from COVID-19, Branswell writes, with low case numbers for a few weeks or months. It’s hard to say whether this “break” will constitute the end of the pandemic, though—we don’t know how long post-Omicron immunity lasts.
- Rapid at-home tests work well at detecting Omicron, though they’re far from perfect. As I’ve noted in past issues, there have been some questions recently about how well rapid antigen tests work at identifying Omicron infections. In a recent Your Local Epidemiologist post, Dr. Katelyn Jetelina walked through the data from several recent studies on this topic. The highlights: rapid tests likely won’t work well in the very beginning of an infection, so wait to test until five days after an exposure; if you test positive, trust the result; test repeatedly for higher accuracy; and, if you have the tests, wait for two negative results before coming out of isolation.
- New CDC wastewater report shows how early Omicron was spreading in the U.S. The CDC published a report this week sharing findings from wastewater surveillance systems in a few states and localities. (Wastewater surveillance means the states are regularly testing samples from sewage to identify coronavirus levels coming from residents’, well, waste.) In New York City, Omicron was first detected in wastewater on November 21, the weekend before Thanksgiving. In California, Colorado, and Houston, Texas, the variant was detected in late November or early December.
- An additional booster shot may not be enough to completely prevent Omicron infection, a small Israeli study suggests. Israel was one of the first countries to offer third vaccine doses to its residents, and now it’s also one of the first countries offering fourth doses. A new study presents the impact of these shots among about 270 healthcare workers. The additional doses produced more antibodies in the patients, but “this is probably not enough for the Omicron,” one of the study’s authors told Reuters—at least when it comes to completely preventing infection.
- But: booster shots still reduce chances of infection significantly, compared to people who are unvaccinated. Another new CDC report published this week compares COVID-19 cases among vaccinated, boosted, and unvaccinated people in 25 U.S. jurisdictions. In late December, after Omicron started spreading widely, adults who were unvaccinated had a five times higher risk of COVID-19 infection compared to those who were fully vaccinated with a booster shot, the CDC found.
- Booster shots also have a huge impact on risks of severe symptoms and hospitalization. One more CDC report released this week: scientists analyzed the impact of booster shots on emergency department visits and other hospitalization metrics in ten states. When both Delta and Omicron were the dominant variants in the U.S., the CDC researchers found, third doses had 94% efficacy rates in protecting people against COVID-related emergency department visits, and 82% efficacy rates in protecting against urgent care visits. Efficacy against hospitalization was also over 90%. In short: if you’re eligible for your booster, go get it!
- Booster shots of Pfizer and Moderna vaccines could be critical for countries that used other brands. Last week, I shared a report that found 22 million mRNA vaccine doses are needed as booster shots in low-income countries, to protect the world against Omicron. This past week, a new study in Nature supported this report: a group of scientists in Hong Kong found that Pfizer doses are safe and highly effective booster shots for people who initially received the Chinese CoronaVac vaccine. The authors suggest that mRNA vaccines should be used as boosters in countries that originally distributed CoronaVac.
- New research identifies a mutation that may contribute to Omicron’s super-contagiousness. A new study from the National Institutes of Health (NIH) found that a mutation present in the Alpha and Delta variants allows the coronavirus to more easily bind to human cells. When the coronavirus binds more easily, it can spread faster within the body; this rapid multiplication helps the virus quickly spread outside the body as well, increasing contagiousness. Though this study was done before the Omicron variant emerged, Omicron has this same mutation, explained lead author Dr. Lawrence Tabak in a post for the NIH Director’s Blog.
More variant reporting
HV.1, JN.1: Variants to watch this fall and how we’re tracking them
As winter approaches, pretty much every public health expert I follow is anticipating a COVID-19 surge. The size and severity of that surge may depend in part on SARS-CoV-2 variants. As a result, experts are closely watching a few current …
National numbers, September 17
For the second week in a row, available data suggest that the current COVID-19 surge may be turning around, or at least heading for a plateau. But there’s still a lot of coronavirus going around—and this will likely remain true …
New data on BA.2.86 suggest the fall booster may work well
Since BA.2.86 emerged a couple of weeks ago, scientists around the world have been racing to evaluate this variant. Several teams posted data in the last week, and the news is promising: while BA.2.86 does have an advantage over past …
Wastewater surveillance is crucial for tracking new variants, BA.2.86 shows us
This week, the health department in New York City, where I live, announced that they’d identified new variant BA.2.86 in the city’s wastewater. I covered the news for local outlet Gothamist/WNYC, and the story got me thinking about how important …
Variant Q&A: Why scientists are concerned about BA.2.86, and which questions they’re still investigating
Last week, I introduced you to BA.2.86, a new Omicron variant that’s garnered attention among COVID-19 experts due to its significant mutations. We’ve learned a lot about BA.2.86 since last Sunday, though there are many unanswered questions to be answered …
BA.2.86 is the latest variant to watch; send me your questions
Last week, several variant experts that I follow on Twitter started posting about a new SARS-CoV-2 variant, first detected in Israel. They initially called it Omicron BA.X while waiting for more details to emerge about the sequence; it’s now been …