As the fall semester nears and universities grapple with what to expect when students return to campus, one study out of the School of Public Health offers a hint of hope. 

The study, led by Public Health professor A. David Paltiel and researchers from Harvard Medical School and Massachusetts General Hospital, found that universities could likely ward off a COVID-19 outbreak by testing students every two days and implementing strict behavioral regulations.

The researchers mapped out how COVID-19 might spread through a hypothetical group of 5000 college students using Microsoft Excel, and analyzed which variables school administrators could manipulate to best avert an outbreak. The study’s authors acknowledged the “existential” threat US universities must now confront: open doors to students and a potential COVID-19 eruption or face the financial fallout. 

The results showed that, with testing, quantity counts for more than quality — in other words, the frequency of testing is the most important variable in preventing on-campus outbreaks. Testing students more often, even with a cheaper and less sensitive test, will weed out coronavirus cases more efficiently than testing less often with a more sensitive test.

Paltiel explained that a 70 percent sensitive test — a test that catches when someone is infected with COVID-19 70 percent of the time — administered each day will catch 100 cases after about three to four days, whereas a 95 percent sensitive test that schools can only afford to administer once per week will take nearly twice as long to catch the cases. 

“Frequency actually makes up for a world of sins in regard to imperfect sensitivity,” Paltiel told the News.

The study showed that the best-prepared college campuses will screen students frequently, isolate infected students within hours and implement strict behavioral guidelines to ensure COVID-positive students don’t spread the disease.

The researchers noted, however, there is a risk of testing too often. Though most commercial tests’ specificities — their ability to detect the absence of a coronavirus infection — are close to perfect, even one or two percent of false positives adds up as schools test thousands of students multiple times per week. 

These false positives can overwhelm the isolation facilities, upset students unnecessarily isolated in a unit with infected peers and undermine confidence in the testing program. The tests Yale will use are said to have a specificity of 99.97 percent, said Albert Ko, department chair and professor of epidemiology. 

Above all, the researchers found that universities could not prevent an outbreak with symptom-based testing alone; they must also screen asymptomatic students. Paltiel likened the approach of testing only students exhibiting symptoms to “bringing a condom to a baby shower.” In the study’s computer simulation relying only on symptom-based testing, by the close of the 80-day semester, the cohort had been overrun with 4970 total infections out of a population of 5000 students. By contrast, screening asymptomatic students every two days resulted in 243 cumulative infections.

Paltiel explained that college-age students often don’t exhibit symptoms — even if they do, the risk of mortality remains low. What students do risk, however, is spreading the virus to more vulnerable members of their community. Therefore, schools that only test symptomatic students could face dire repercussions that stretch beyond their campus gates.

“You don’t plan a safety net that can only be as strong as what you think it’s going to have to withstand,” said Paltiel. “It does trouble me that many colleges out there are doing the absolute minimum, banking on the planets to align and hoping against hope that everything that could go wrong will go right. I don’t think that’s any way to treat our kids, or the staff, the custodians, the dining hall workers, the person who works at the Starbucks on Chapel Street — there’s a much broader community of people who could potentially be harmed if something were to go awry.”

Or, as he put it more simply: “A bridge that can only withstand the weight it expects to bear is called a house of cards.” 

Though public health experts have pored over the available data in an effort to predict how the term will play out, no one can be entirely sure. With his past models, sometimes reality has matched the predictions, but sometimes the two did not line up, Paltiel explained.

An ever-growing number of universities have called off an in-person semester; on Monday, the University of North Carolina at Chapel Hill sent students home after the coronavirus ripped through campus, infecting at least 130 students during the first week of classes. But University President Peter Salovey reaffirmed in a Friday email that most Yale undergraduates would start the term on campus.

The researchers noted that though the study outlined a way to contain the number of COVID-19 infections, the high bar may be out of many schools’ reach. Colleges face the challenge of getting college students to obey public health protocols. Schools must also overcome financial obstacles. Universities would need some 195,000 test kits to screen a 5,000-student cohort every two days during the fall semester and such frequent testing is costly. 

Yale has contracted the BROAD Institute of MIT and Harvard to provide PCR testing for undergraduates. The Institute boasts a 24-hour turnaround time for test results, according to its website. The BROAD provides tests at cost, charging between $25 and $30 per test — less than half of what some commercial tests can fetch — in a bid to provide testing to hospitals, homeless shelters, high-impact communities and universities.

Still, the front end of expenses falls to Yale, with the University shelling out hundreds of thousands of dollars, potentially millions, to set up eight new testing sites within residential colleges and hire extra staff, Dean of the School of Public Health Sten Vermund said.

“I don’t think Yale is being irresponsible … I think we’re making the investments to keep people safe,” Vermund said. “Three months from now I hope I’m not proven wrong, but we’re trying to make the best judgment on behalf of what’s good for our students and our broader community.”

In an invited commentary accompanying the study, Elizabeth Bradley, President of Vassar College and founder of the Yale Global Health Leadership Institute, said that testing every two days may not be necessary. Bradley wrote that “one size does not fit all” when it comes to containing COVID-19. Rather, schools should take different approaches based on their individual circumstances. Vassar, which will limit student movement off campus and require negative tests before students arrive, plans to test students less frequently. 

Yale is also diverging from the study’s suggestions, opting to test students twice weekly and to implement a contact tracing program. Vermund explained that contact tracing can catch students exposed to COVID-19 while the virus is incubating and tests cannot yet detect it.

Ko explained that the high sensitivity reported for PCR tests is their ability to diagnose COVID-19 when people are sick with the disease. The tests are effective at diagnosing someone severely ill with COVID-19, but the “jury’s still out” on exactly how well the test detects the virus in someone who’s asymptomatic, Ko told the News.

“You can imagine if somebody at Davenport has been exposed, they don’t reach that peak viral load immediately,” Ko said. “Actually they are negative, the tests won’t pick them up during the incubation period or at least for the first several days after infection.”

But with repeat testing, near-perfect sensitivity becomes less vital, as the tests will ultimately catch someone infected as their disease progresses.

Importantly, when it comes to COVID, there is no ‘Yale-only’ bubble. An outbreak anywhere in the region could place the University at risk, forcing a school shutdown before the virus comes to campus.

“With the frequent testing I’m positive that we’re going to be able to detect outbreaks, hopefully we’re going to be able to control them, but what I’m really kind of concerned about is not just what’s going to happen here at Yale, but what’s going to happen in Connecticut, in the region,” Ko said. “If we have a big outbreak in New York, I think we’re going to have to make hard decisions and hard looks at what we’re going to do here in Connecticut.”

Additionally, because the campus is intertwined with the city — even bisected by Elm Street — though undergraduates are tested every few days, there are large swaths of city residents and sophomores living off campus who the school won’t test and who could possibly be part of an outbreak, Vermund added. 

The long-term success of Yale’s plans to avert an outbreak hinges on whether students adhere to the school’s “community compact.” Before returning to campus, undergraduates must sign onto the document, pledging to wear masks and follow group gathering protocols.

But opinions differ as to whether students will cooperate with protocols, a doubt Vermund dubbed the “million-dollar question.” 

For his part, Paltiel fears that if students are prohibited from all social interaction and intimacy, they will still go to parties — though under the school’s radar and without any distancing.

“What scares me is the party in a crowded basement on High St. and nobody wearing masks,” Paltiel said. “It’s on me, it’s on the schools to provide [students] with imaginative, compassionate, realistic, low-risk ways you can stay sexually active, socially connected, and get the Jello shots you need, all without having to crowd into a poorly ventilated basement with nobody wearing masks or washing their hands at the frat house keg party.”

Paltiel stressed the importance of harm reduction: if “bending the rules” or turning a few blind eyes to smaller risks keeps students safe from the greater risk of COVID-19, it’s worth it.  

But Pericles Lewis, Vice Provost for Global Strategy and chair of the residential and extracurricular  contingency planning committee, wrote to the News that he believes that students will abide by the compact, as Yale students “care about the health and safety of others.” He added that the University is recruiting student public health educators, who will help their peers grasp the importance of the compact.

In a July 1 email to Silliman College residents when Yale first announced its plan to reopen on-campus housing, Head of College and psychology professor Laurie Santos warned Yale’s “community compact” was not to be taken lightly, treated like some course readings and skimmed for main ideas. She explained that some staff members are from sectors of society that are particularly vulnerable to COVID-19, and that they do not have the choice of whether to come to campus. At the time, Yale was planning to test returning students once per week — a plan that the University modified several weeks later, when it announced that it would instead test students twice weekly.

“We all should be emotionally prepared for widespread infections — and possibly deaths — in our community,” Santos’s email reads. “You should emotionally prepare for the fact that your residential college life will look more like a hospital unit than a residential college.”

Paltiel’s study is situated in this world of unknowns and, because of that, is not prescriptive. The study doesn’t take sides or mandate a clear path forward, Paltiel stipulated, neither advocating for colleges to open nor to keep their gates shut.

“I really do want to leave it as a question that I pose to university administrators, to college students and to their loved ones,” Paltiel said. “Ask yourself: can we meet these minimal standards, and if we can’t, do we have any business reopening?”

Fall classes at Yale College begin on Aug. 31. 

Rose Horowitch |

Clarification, Aug. 18: This article has been updated to contextualize when Santos’ email was sent to Silliman students.

Rose Horowitch covers Woodbridge Hall. She previously covered sustainability and the University's COVID-19 response. She is a sophomore in Davenport College majoring in history.