A new paper co-written by a team of Gies College of Business professors shows that rapid bulk-testing for COVID-19 along with other standard mitigation measures such as mask-wearing and social distancing were the keys to successfully reopening colleges and universities during the novel coronavirus pandemic.

For institutions of higher education that chose to reopen for full-time, in-person classes in the fall 2020 semester, investing in COVID-19 tests that were cost-effective, easy to administer in high volumes and yielded quick results was the key element in managing the epidemic on college campuses, says a study co-written by Ujjal Kumar Mukherjee, a professor of business administration at the Gies College of Business at Illinois, and Sridhar Seshadri, the Alan J. and Joyce D. Baltz Endowed Professor at Illinois.

Mukherjee and Seshadri’s co-authors are Subhonmesh Bose, Anton Ivanov, Sebastian Souyris, Ronald Watkins and Yuqian Xu of the University of Illinois Urbana-Champaign; and Padmavati Sridhar of the University of California, Berkeley.

The paper, published in the journal Nature Scientific Reports, analyzed data from 86 institutions, including the Urbana campus’ SHIELD Illinois testing program. The study combined the analysis with a small sample-based analytical model of infection dynamics and an agent-based simulation experiment to study the efficacy of various collegiate reopening strategies.

The combination of the small-sample dynamics with the agent-based simulation provided an estimation of the range of likely scenarios that administrators could expect under different levels of testing and mitigation strategies such as mask-wearing, social distancing and contact tracing, the researchers said.

“The idea with this paper was to see how universities fared in reopening last fall for in-person classes and analyze the effectiveness of their plans for testing and their control mechanisms,” said Mukherjee, an expert in supply chain logistics and innovation in health care. “The importance of opening up for in-person classes was never in question. A number of things at a university can’t be done remotely. Labs, for example, are so important to the in-person student experience at a university. So the question was, how can you open up and still be safe? That prompted us to analyze the various reopening strategies that different universities adopted.”

The researchers found that while preventative measures such as mask wearing, social distancing and a reduction of contact rates among individuals were indispensable to reopening and reducing the asymptomatic spread of COVID-19, those measures were insufficient on their own to contain the virus.

“According to our analysis, frequent bulk surveillance-testing” – that is, testing everyone once every few days – “that yielded quick results in combination with masks, distancing, contact tracing and rapid isolation of positive cases was crucial to containing transmission,” Mukherjee said. “The key design parameter was the ratio of the total number of daily tests to the institution’s population,” said Seshadri, an expert in information systems and operations management. “Additional measures can help combat the disease propagation, such as testing certain subgroups more frequently and increasing the efficiency of isolation of patients who test positive. But ultimately you need testing technology that can provide test results quickly.

“You would rather have tests that give quick results less accurately than more accurate tests with slower and delayed results.”

But rapid COVID-19 testing can be expensive and difficult to implement at scale in every institution, the researchers said.

“If you can’t test at sufficient numbers to open up an institution completely, then you have to calculate how many members of the institution you can safely allow on campus,” Seshadri said. “In other words, what percentage of members need to be tested every day so that, when you combine testing with mitigation measures, you can safely reopen. We found that it’s important to consider a ratio of the total number of tests to the total population of how many students you expect to be on campus.”

“You can either work on the numerator – change the total number of tests – or you can work on the denominator, which is the total number of people on campus,” Mukherjee said. “If you have a fixed number of tests, you would need to work on the denominator and essentially limit how many people can come to campus. But if you’re able to test at least 20% of your population on a daily basis – essentially, once a week testing of every individual – then you can have a reasonable expectation of safety. Beyond the 20% threshold, however, you only see marginal benefits to safety.”

The second most important finding from the study is that not one single strategy works on its own, the researchers said.

“You have to employ a multilayered mitigation approach – that is, all the different strategies of testing, masks, distancing and quarantining positive cases working together in concert,” Seshadri said.

“Each layer of protection effectively reinforces the other,” Mukherjee said. “If you think that because you’re testing everyone that you don’t need to enforce masking or distancing, then it all falls apart. The multilayered approach is a strategy that we validated in the paper.”