Chicago public health officials say that COVID-19 cases caused by the delta variant are rapidly increasing in the city, and that by next month the strain will likely be the dominant form of the virus in the city.
During a press availability on Tuesday, Dr. Allison Arwady, the commissioner of the Chicago Department of Public Health, said that the delta variant is causing approximately 44% of the COVID cases in the city, and that officials expect that the variant will surpass the 50% mark next month.
“One thing that we are seeing with the major surges (is that) it is being driven by the delta variant,” she said.
Delta variant is 50% more contagious than the alpha variant, which originated in the United Kingdom. That strain was 50% more contagious than the initial strain of COVID-19, according to Arwady.
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She explained that individuals who become infected with the delta variant are generally expected to infect twice the number of people than they would if they contracted the alpha variant.
“Delta is on the increase here because it is more contagious. Where there are no masks or no vaccines, somebody with the original version of COVID would transmit it to about two other people. The delta variant, in the absence of masks or any mitigation would instead transmit to more like three to four people,” she explained. “That may not sound like a lot, but transmission to two people means you’re doubling your (cases), and transmission to potentially four people really sees an exponential rise very quickly.”
Arwady cautioned that data has not conclusively shown that the delta variant causes more severe cases of COVID, saying that the main conclusion at this stage is that the variant causes more infections because it is more contagious than previous strains, but officials say that the increase in cases can be stemmed so long as people continue to receive their COVID vaccinations.
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“We have three different vaccines readily available to all of our residents, which offer very good protection against delta and other variants,” Chicago Mayor Lori Lightfoot said. “We’re seeing an increase among unvaccinated individuals and in areas of low vaccination rates, locally and throughout the U.S. Nearly all COVID-19 hospitalizations and deaths are occurring in unvaccinated people, meaning this pandemic is now targeting the unvaccinated.”
According to studies, both the Pfizer and Moderna vaccines, which require two doses, have been found to be 84% effective at preventing COVID cases that stem from the delta variant. Studies have also shown that the vaccines are highly effective at preventing hospitalizations.
The Johnson & Johnson vaccine, which requires one dose, appears to show “strong, persistent” protection against the delta variant, according to the company.
