On July 31, three researchers associated with the Yale School of Public Health and Harvard Medical School published an article in the JAMA Network Open (the Open Journal of the American Medical Association). This article described a study outlining a simulation the Yale and Harvard researchers developed to determine what would be needed in order to operate a college campus safely this fall.
The design of the simulation assumed a cohort of 5,000 students. All but 10 students would be without SARS-CoV-2 infection, and 10 of the students would have an undetected, asymptomatic SAR-CoV-2 infection at the start of the semester. The model was linked to a compartmental epidemic model to evaluate symptom-based screening and tests of varying frequency (i.e., every 1, 2, 3, and 7 days), sensitivity (i.e., 70% – 99%), specificity (i.e., 98% – 99.7%), and cost (i.e., $10/test – $50/test).
In addition, three virus reproductive rate scenarios were defined. The model assumed an 80-day, abbreviated Fall 2020 semester.
The researchers concluded that screening every two days using a rapid, inexpensive, and even poorly sensitive (>70%) test, coupled with strict behavioral interventions to keep the reproductive rate at less than 2.5, is estimated to maintain a controllable number of COVID-19 infections and permit the safe return of students to campus.
Among the items that I found fascinating in the model input parameters and scenarios were the following:
- Mean incubation time – 3 days
- Time to recovery – 14 days
- Time to false-positive return – 1 day
- Exogenous infections per week – Best (5), Base (10), and Worst (25)
- Probability of symptoms given infection – 30%
- Time to test result return – 8 hours
The researchers assumed that after a lag of 8 hours, individuals receiving a positive test result (true or false) and those exhibiting COVID-19 symptoms would be moved from the general population to an isolation dormitory from which no further transmissions would occur. The lag reflected test turnaround delays and the time required to locate and isolate identified cases.
Various findings surfaced under each scenario. For example, if daily tests were conducted, fewer students with actual COVID-19 infections were residents in the isolation dorm. The more days that elapsed between student body testing (up to every 7 days), the higher the percentage of students in the isolation dorm who were actually COVID-19 infected.
With weekly screening, nearly the entire student population would be infected before the conclusion of the 80-day semester. During the 80-day semester, the per-student costs of implementing the preferred screening strategy were $120, $470, and $910 in the best, base, and worst-case scenarios.
The researchers stressed the importance of minimizing the transmission potential of infection by following social distancing and other guidelines. Specifically, the researchers mentioned the importance of:
- Handwashing frequently
- Mandated indoor masking
- Elimination of buffet dining
- Limited bathroom sharing with frequent cleaning
- De-densifying campuses and classrooms, and other best practices
The researchers note that obtaining an adequate supply of testing equipment will be a challenge. With a population of 5,000 students as used in the simulations, screening students every two days will require more than 195,000 test kits during the 80-day semester.
With a range of $10-$50/kit, that is a cost of $1.95M – $10M for test kits only during the semester. The Yale and Harvard researchers conducted a cost-effectiveness analysis and compared their findings with an estimate of the societal willingness-to-pay (WTP) per infection avoided. They also note that their model did not include the impact of transmissions exported off campus.
Elizabeth Redden wrote about this Yale and Harvard study in the August 3 issue of Inside Higher Education. She interviewed Dr. David Paltiel, the study’s lead author, who acknowledged that the study’s recommendation of testing every two days “may well be beyond the capacity of many schools.” While the cost of testing every 1, 2, or 7 days were $120, $470, or $910 per student for the semester, the study’s authors found that there is “no circumstance in this modeling study under which symptom-based screening alone would be sufficient to contain an outbreak.”
Commenters were invited to review the findings and one author of a commentary, Dr. Elizabeth H. Bradley, is a public health scholar and also the president of Vassar College. Dr. Bradley says it is likely that colleges are not planning for enough testing, since the “every two days” recommended testing cycle exceeds the Centers for Disease Prevention and Control (CDC) recommendations.
At the same time, she states that taking strong steps to limit the rate of transmission by limiting the movement into and out of campus could bring down the testing burden. While the base case uses a rate of transmission of 2.5, Dr. Bradley and her co-commenters write that colleges that can achieve adherence to behavioral guidelines may be able to bring the rate of transmission down to 1.0 to 1.5.
Vassar is using a rate of 1.25 for their planning purposes. With this rate of transmission, Vassar believes that they could control the infections even if they tested every four weeks.
As Dr. Paltiel and his colleagues write, the simulations are designed to see if a campus of 5,000 can contain the spread of the COVID-19 virus. When I look at their published outcomes under the multiple scenarios and read the Inside Higher Education article that offers additional commentary, I believe that many colleges and universities will be unable to contain the spread of the COVID-19 virus.
While social distancing may possibly be maintained in all of the campus buildings, any campus with a substantial percentage of students who live in off-campus housing or who visit off-campus bars and restaurants will likely be unable to control the spread. I base my conclusion on my experiences as a college student, my friends’ and colleagues’ experiences as college students, and the fact that I have two daughters who are currently college students.
In my opinion, few universities announcing a return to campus will make it through the entire fall semester in the same form and frequency of instruction as they started. The consequences will impact higher education for many years.