The Daily Explains: Updated city, state COVID-19 guidelines in light of omicron subvariant prevalence


Seeger Gray/The Daily Northwestern

Policy changes from the CDC and federal HHS have changed how the city and state measure local transmission levels.

Angeli Mittal and Alex Harrison

Evanston stopped publishing COVID-19 test positivity rates April 28 due to shifts in federal reporting requirements, according to Health and Human Services Director Ike Ogbo. 

The change occurred shortly before a recent rise in positive cases, with Evanston and Northwestern both recording more than 300 new positive cases in a single week. In an email to The Daily, Ogbo said the Illinois Department of Public Health — and by extension, the city — is no longer able to measure the city’s positivity rate. 

Ogbo said this is because the U.S. Department of Health and Human Services dropped its requirement for testing centers to report negative results for rapid and antigen tests. 

“Evanston is inclined to use the new federal guidelines for tracking COVID-19 at the community level as we continue to provide weekly reports,” Ogbo wrote.

Ogbo has not yet responded to a further request for comment about the city’s shift in published COVID-19 data from new cases and positivity rates to hospitalizations and case rates per capita.

The U.S. HHS announced the policy change March 8, and it went into effect April 4. Because the IDPH no longer receives the complete sample of test results over a given period, it cannot derive a positivity rate representative of a population’s caseload over time.

Ahead of the federal announcement, the Centers for Disease Control and Prevention released a new Community Levels framework Feb. 25 with updated guidelines and criteria for communities to evaluate their local transmission levels.

Previously, frameworks such as Chicago’s Community Transmission and Risk Matrix focused on nominal new positives and positivity rates. However, the Community Levels framework is based on three factors: the number of new COVID-19 cases per 100,000 people, COVID-19 hospitalization and average hospital bed occupancy over the previous seven days. Based on whichever of these metrics is highest, communities are labeled with a “Low,” “Medium” or “High” level of transmission.

The CDC publishes updated daily Community Levels for each U.S. county based on that day’s reported data. Evanston announced its move to a “Medium” transmission level Thursday due to an influx of COVID-19 positive cases reported the previous week, for which the CDC recommends considering testing strategies for individuals exposed to the virus. 

Though 66.3% of the U.S. population 5 years and older is fully vaccinated — compared to 88.4% of Evanston and 73.2% of Illinois  — newer omicron subvariants are more likely to cause breakthrough infections in vaccinated or previously-infected people than other variants, according to the CDC. 

On April 26, the CDC estimated that by the beginning of February, 58% of the U.S. population had contracted COVID-19 since the start of the pandemic in March 2020, up from 34% in December 2021.

With the timeframe for the graph beginning a few weeks before the first sequenced omicron case in the Chicago area, delta, five prevalent omicron subvariants and other subvariants not listed are depicted. Data courtesy of the Center for Pathogen Genomics and Microbial Evolution in the Havey Institute for Global Health. (Angeli Mittal/The Daily Northwestern)

In a campuswide May 5 email, NU’s Vice President for Operations Luke Figora said the University will continue to release weekly case numbers and positivity rates every Friday as it has since November 2020. NU does not use the Community Levels framework or report hospitalizations, and retired its own Campus Activity Levels framework March 4. 

“Absent any major changes to the impact of the pandemic on our community, we will maintain our current approach through the end of the academic year,” Figora wrote. “We will assess our needs over the summer in consultation with public health officials and our own medical experts.”

Email: [email protected]

Twitter: @amittal27

Email: [email protected]

Twitter: @alexhairysun

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