Though Chicago is seeing a steady increase in COVID-19 cases amid emerging omicron variants, health officials don't expect a major surge similar to other U.S. cities over the past weeks.
Chicago Department of Public Health Commissioner Dr. Allison Arwady said Thursday that because the city and the Midwest saw bigger spikes in coronavirus cases with the original omicron variant, BA.1, than other cities, more Chicagoans are protected against new strains.
"If you had a breakthrough infection, you know in that January time period, that most likely was Omicron. You have additional protection - we expect not 100% protection, but good protection against BA.2," Arwady said. "That paired with being up to date with your vaccines should help keep this in control in Chicago and across the whole Midwest. BA.2 is now making up more than two thirds of our patients."
Arwady noted that omicron's BA.2 variant makes up about 67% of COVID cases in Chicago and approximately 72% of cases across the country. In the northeast, where cities are seeing large increases, over 80% of cases - near 90% - are the BA.2 strain.
Chicago's top doctor said earlier this week that she's also not yet concerned about a new hybrid COVID variant known as XE spreading in the United Kingdom, which is making plenty of headlines with concerns about its transmissibility.
"Mostly, it's been detected in the UK, several hundred cases, but nothing at this point that is clearly showing major concern or spread," Arwady said in a statement. "And so it hasn't even been labeled at this point, an official variant of interest."
Arwady noted that while the recombinant variant has been detected in the U.S. already, no cases have been reported in Chicago or Illinois as of Monday.
"Whenever you see a new variant emerge, the main thing is it's got... it may have some little advantage, maybe a little more contagious, but no, this is not one at this point that I have any specific concern about," she said. "It remains sort of a version of omicron."
The XE variant is a recombinant, meaning it has parts of two different variants rearranged into a new virus, which in this case are BA.1, the original strain of omicron, and BA.2, known as "stealth omicron."
It was first detected in mid-January in the United Kingdom, where more than 600 cases have been reported since, according to the UK's Health Security Agency.
According to the Chicago Department of Public Health, a handful of XE cases have been reported outside the U.K., including in the U.S.
Recombinant variants themselves are not out of the ordinary, according to health officials.
"Recombinant variants are not an unusual occurrence, particularly when there are several variants in circulation, and several have been identified over the course of the pandemic to date," Hopkins said. "As with other kinds of variant, most will die off relatively quickly."
In the U.K., health officials are monitoring two other recombinants: XD and XF, which consist of genetic material from the Delta and BA.1 strains, as well as the XE variant.
According to the CDC's website, XE isn't currently being monitored by U.S. epidemiologists nor has it been labeled as a "variant of interest" or "variant of concern."
WHO said it will continue to study recombinants and provide updates as further evidence becomes available.
XE might be the fastest-spreading strain yet, according to preliminary research, but studies are underway to determine the exact contagiousness of the variant.
Early growth rates of the variant weren't significantly different from BA.2, the UK Health Security Agency initially said. However, in an update on March 25, health authorities revealed more recent data showed XE had a growth rate of 9.8% above BA.2.
WHO released similar information, citing estimates that show XE is 10% more transmissible than BA.2. However, those findings require further confirmation, the agency noted.
BA.2 was previously identified as the most transmissible variant as it spreads about 75% faster than BA.1, according to health officials.
"Any time there is a more transmissible virus, it has the chance of becoming the predominant virus across the world," said Hannah Barbian, a genomic epidemiologist at the Regional Innovative Public Health Lab at Rush University Medical Center.
Experts said COVID vaccines have been effective against all variants that have surfaced, when it comes to preventing hospitalizations and death. More studies, however, are needed to see what impact vaccines could have on the XE variant.
So far during the pandemic, new strains and surges have hit Europe and China first, which is why scientists are watching what happens there closely.
"The U.S. hasn’t seen evidence for a new surge yet, so I think this could be the exception. We’re not sure, but I think we always want to know viral dynamics in our area," said Barbian.