County COVID breakthrough cases undercounted, but university offers more accurate numbers

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Because the Centers for Disease Control and Prevention (CDC) only requires healthcare administrators to report severe infections of COVID-19 among the fully vaccinated, the true number and percentage of vaccine breakthrough cases infections in Champaign County and across the nation is significantly undercounted, public health experts say.

However, data on campus Covid cases at the University of Illinois at Urbana-Champaign from its SHIELD testing system, gives some idea of how prevalent COVID-19 cases can be among a vaccinated population and how deep the undercount may be in the county, state and nation. 

A breakthrough infection is defined as a case of COVID-19 detected in a person who tests positive two weeks or longer after receiving their second dose of the vaccine, according to the CDC. So far, the severity of COVID-19 symptoms for the vaccinated is still significantly less than those who are unvaccinated.

Since late April, the Illinois Department of Public Health has received breakthrough case data from healthcare administrators regarding severe breakthrough cases, or cases that lead to hospitalization or death. 

Numbers show that since then, over 3,000 hospitalizations and 1,000 deaths occurred in fully vaccinated COVID patients in Illinois. The percentage is only a small percentage — less than 0.1% of the fully vaccinated population

Data from the University of Illinois shows that breakthrough cases — severe and mild — are much larger than than the state numbers. Since May, 75.9% of, or more than three out of four, positive tests belonged to fully vaccinated students or staff. 

Champaign County public health officials say 18% of cases are breakthrough cases, but acknowledge that is an undercount.

By April 31, 2021, just weeks after the publicly available vaccine rollout, the CDC recorded over 10,000 instances of breakthrough cases across the nation.

In the report, the CDC notes, “The number of reported COVID-19 vaccine breakthrough cases is likely a substantial undercount of all SARS-CoV-2 infections among fully vaccinated persons,” due to the constraints of a system that relies on passive and voluntary reporting. 

Yet, the following day, the CDC transitioned from monitoring all breakthrough infections to only monitoring those which result in hospitalization or death. 

Following CDC guidelines, state health departments are encouraged, but not required to report breakthrough cases on a voluntary basis. State health departments and the CDC rely on healthcare administrators to report breakthrough cases in instances that lead to hospitalization or death. These cases are reported to a Vaccine Adverse Event Reporting System.

Because of this, there is no sure measurement of the total number of mild breakthrough infections, nor the likelihood of them, throughout the state of Illinois and across the nation. 

However, the University of Illinois is able to to cross-reference vaccination records with positive PCR tests through its SHIELD Testing System to indicate which infections constitute breakthroughs. The University receives vaccination records for students and staff directly from the Illinois Department of Public Health vaccination database. 

Though the University reports testing and vaccination data on its SHIELD Testing Data Dashboard, it has not yet implemented a space for breakthrough cases to be portrayed. 

 “The university doesn’t currently have breakthrough cases displayed on the dashboard, but that is something that has been requested,” said Vice-Chancellor of the University Mike DeLorenzo. The breakthrough case data can currently be accessed by filing a Freedom of Information Act request to the University. 

Currently, the University requires all students and staff to be fully vaccinated for COVID-19 unless exempted for religious or medical reasons. Thus, the high volume of breakthrough cases recorded on campus is an expected result of a community with high rates of vaccination, public health officials say 

“The guidelines for faculty, staff, and students are the same. Everyone must be fully vaccinated or have a medical or religious exemption. Those who are not fully vaccinated are required to test every other day to stay in compliance. Those who do not comply will face disciplinary action,” DeLorenzo said. 

“In the case of the University, the breakthrough cases are much higher in the campus community, and the reason for that is because almost everybody is fully vaccinated,” said Awais Vaid, deputy administrator and epidemiologist at the Champaign-Urbana Public Health District. The data cross-referenced from IDPH shows that as of December 5, 95% (29,411) of undergraduate students, 97% (10,535) of graduate students, and 89% (9,324) of faculty and staff are fully vaccinated. This is higher than the Champaign County average, which is slightly more than 60%.

Most breakthrough cases on campus were detected in those fully vaccinated with Pfizer. Of the 1,214 new cases reported on campus from May to November, 921 occurred in people who were fully vaccinated: 

  • 56% of breakthrough infections occurred in those vaccinated with Pfizer
  • 27% occurred in those with Moderna
  • 12% occurred in those with Jannsen. 
  • The remaining 5% can be attributed to other vaccines such as AstraZeneca or Sinopharm. 

“Nationally, and even in Champaign County, we have seen higher breakthrough cases with the Pfizer vaccine,” Vaid said. He also said some people who were fully vaccinated with Pfizer switched to Moderna for a booster shot after national and county studies also suggested more breakthrough infections lived in Pfizer recipients. 

Because viruses mutate over time, certain strains of COVID-19, such as the delta variant are also more likely to break through vaccines.

 “The strands of viruses change just a little bit. This is exactly the same thing that happens with the flu every year,” Vaid said. “The reason we have to take a vaccine like the flu shot every single year is because of small changes.” 

This may raise concern over new variants, such as Omicron.  

In order, the top three weeks of the semester with the most recorded positive breakthrough cases were: 

  • August 29 to September 4 with 251 new cases 
  • October 31 to 6 November with 176 new cases
  • August 22 to 28 with 157 new cases 

The semester’s top weeks for positivity closely neighbor two events that gather large crowds: move-in weekend and Halloween. Because the University is tracking breakthrough cases, leadership is able to adjust policymaking based on the science. 

“Our SHIELD Team did notice an increase of cases after Halloween, a trend seen in the rest of the state as well,” Vice Chancellor DeLorenzo said, “To prevent spread, the chancellor urged everyone (fully vaccinated included) to be tested at that time.” 

New recommendations were set in place which encouraged students to test before and after fall break, regardless of their vaccination status.

Last year, students were instructed not to return to school after traveling home between Thanksgiving and winter breaks. DeLorenzo said the university recommends vaccinated individuals get tested before and after travel, if symptomatic, and if they have been identified as living in an area with an increased number of cases. 

Recommendations for the fully vaccinated to test are relatively unique to the University community and are another reason for its higher and more accurate count of breakthrough cases compared to the rest of the state and nation. 

Though the University has not yet published breakthrough case data, the Champaign-Urbana Public Health Department does include breakthrough case data on one of its public dashboards, The COVID-19 Vaccination Data Dashboard. 

Since March 2020, the health district has publicly listed positive test data and demographics on its website. 

“It was important for us to be transparent and educate the community on their risk,” Vaid said about the public dashboards. “The community is trusting that we are sharing everything as we are receiving it so there’s nothing they need to FOIA or have special requests made for this data.” 

The district began reporting breakthrough case data daily on July 1. 

“Our goal every morning is to make sure that every single positive case that has shown up in our system is investigated by the end of the day,” Vaid said. 

The dashboard is updated on multiple data sources including hospital data, local case data, and the state public health website. The local health district receives data through the “Disease Reporting System, and an investigation is started. The district also uses the state vaccination record database to cross-verify any breakthrough cases. 

Since July, 18% of all positive cases in the county have belonged to the fully vaccinated community, the health district said. However, this is likely an undercount compared to the University’s data. The contrast between this number and the University’s 75.9% are due to the County’s much-lower vaccination rate of 60%, and the ability and encouragement for fully vaccinated individuals to test on campus, even when not symptomatic. 

Vaid noted this number is likely an undercount based on increased testing in the University community and the county vaccination rate. He also noted that rates have changed over time. 

“The monthly rate changes as well. Our breakthrough rate in July was about 10-12% and in November it was about 25% and in December it is back to 15%,” he said. 

Though there are likely more breakthrough cases than are being reported, vaccine efficacy considers many factors, such as transmission rates and symptoms. It is still highly recommended to get vaccinated. Of the minute amounts of fully vaccinated patients who were hospitalized from COVID-19 in Illinois, 72% were over the age of 65 and 50% had an underlying health condition. 

In all data provided across states, hospitals, and health departments, the majority of hospitalizations occur in those who are unvaccinated, and fully vaccinated individuals still have a lower chance of contracting COVID-19 than unvaccinated individuals.

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