As SARS-CoV-2 was detected in the US, emergency public health measures took effect, including shutting down schools.1 As prevention and control measures improved, emergency response policies were rolled back.1 Cornell University opened for residential instruction in Fall 2021 using an extensive testing, contact tracing, and isolation program in partnership with the Tompkins County Health Department (Table).2 Vaccination was mandated for all students and encouraged for employees. Masks were required on-campus, and isolation orders and contact tracing occurred within hours of any positive result. We hypothesized that these measures would limit COVID-19 spread on campus and sought to monitor this with a case-series study of university testing records.
For the Fall semester (August 26 through December 18, 2021), all undergraduates (15 503 students), 2873 graduate students (28.5%), and 2803 employees (20.9%) were required to register for and participate at least once a week in free, on-campus polymerase chain reaction COVID-19 surveillance testing.2 Using a case series approach, all deidentified university surveillance data (ie, test registration, result) were reviewed daily to detect sentinel events and outbreaks and to guide public health responses; testing compliance rate, test positivity rate, and incidence were monitored. Routinely, positive specimens were sequenced for genetic characteristics. As part of Cornell University’s institutional operations, this public health surveillance effort was not subject to institutional review board review, and informed consent was not needed because data were nonidentifiable counts. This study followed the reporting guideline for case series.
When students returned to campus (mid-August 2021), reentry testing was used to identify COVID-19 cases (Figure).3 Isolation, case investigation, contact tracing, quarantine, and targeted supplemental testing limited the outbreak to 480 cases (August 23 to September 10: mean [SD] 22.9 [18.8] cases/d). Thereafter, routine surveillance and public health measures limited transmission (September 12 to November 27: students, 1.9 [2.2] cases/d; employees, 2.4 [2.5] cases/d; 330 total cases; 0.1% positivity) (Table).
After Cornell’s 5-day Thanksgiving break, surveillance outcomes changed dramatically among students (Figure): 75 cases from November 28 to December 4 (mean [SD], 10.7 [6.9] cases/d; 0.5% positivity), 655 from December 5 to December 11 (93.6 [75.7] cases/d; 2.9% positivity), and 1559 from December 12 to December 18 (222.7 [138.7] cases/d; 5.7% positivity). Support teams helped cases isolate safely, investigation identified exposures, and contact tracing identified contacts who were instructed to monitor for symptoms, test, and/or quarantine.
From November 28 to December 31, 2797 COVID-19 cases were identified (mean [SD], 82.3 [82.4] cases/d; 3.1% positivity; 89.0% students, 11.0% employees), eclipsing previously measured incidence. Most cases (82.2%) reported mild symptoms (no reported hospitalizations). Despite high vaccination rates (97.9% of campus3), 98.6% of cases were breakthrough infections, and proportionately more named close contacts who became COVID-positive in this period (22.6%) than previously (4.4% between August 23 and November 27). Something had clearly changed in the university setting, as similar outbreaks were not yet being seen in the off-campus community or neighboring counties.4
From mid-November, positive samples were screened for S gene target failure as a marker of variant Omicron.5 Whole genome sequencing confirmed the presence of Omicron in samples from December 1 (1 sample), December 2 (1 sample), December 3 (2 samples), and December 4 (4 samples). By December 11, 155 of the 174 positive samples (89.1%) were confirmed as Omicron; the Delta variant was detected in the remaining samples.
Given identification of Omicron and the noted speed of transmission, on December 10 university leadership limited in-person interactions, and on December 14 student gatherings were prohibited, examinations were moved online, and an exit testing process was implemented.2 The de-densification process decreased student cases numbers,3 but incidence among people who stayed locally remained higher than before Thanksgiving (December 26 to December 31: students, 11.5 [9.4] cases/d; employees, 16.0 [12.9] cases/d; 4.8% positivity).
The Omicron variant is highly transmissible, particularly in high-density social settings.5,6 Based on analysis of routinely collected population surveillance data, Cornell’s experience shows that traditional public health interventions were not a match for Omicron. While vaccination protected against severe illness, it was not sufficient to prevent rapid spread, even when combined with other public health measures including widespread surveillance testing. Generalizability of the study finding might be limited due to the demographics of its sample (the majority of participants were undergraduate students) and by the study’s single institutional setting. As SARS-CoV-2 continues to adapt, surveillance and case-series studies that look across different populations and settings will be helpful in identifying sentinel events and guiding actions to mitigate harm.
Accepted for Publication: March 31, 2022.
Published: May 18, 2022. doi:10.1001/jamanetworkopen.2022.12906
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2022 Meredith GR et al. JAMA Network Open.
Corresponding Author: Genevive R. Meredith, DrPH, MPH, Cornell University, Schurman Hall, S2-005, Ithaca, NY 14853 (grm79@cornell.edu).
Author Contributions: Drs Meredith and Warnick had full access to all of the deidentified data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Meredith, Frazier, Henderson, Koretzky.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Meredith.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Meredith, Frazier, Wan.
Obtained funding: Frazier.
Administrative, technical, or material support: Diel, Koretzky, Warnick.
Supervision: Meredith, Diel, Frazier, Henderson, Warnick.
Conflict of Interest Disclosures: Dr Frazier reported serving in a leadership role in the Cornell COVID-19 Mathematical Modeling Team, which advises the Cornell administration on its COVID-19 mitigation strategy. No other disclosures were reported.
Funding/Support: A National Science Foundation grant (No. CMMI-2035086) partially supported Dr Henderson’s efforts in design and control of the study. The Air Force Office of Science Research (grant No. FA9550-19-1-0283) supported Dr Frazier and Mr Wan’s efforts in collection, management, analysis, and interpretation of the data.
Role of the Funder/Sponsor: The National Science Foundation and Air Force Office of Science Research had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. The Cornell University Provost’s office facilitated the design and conduct of the study through fiscal support as part of Cornell University’s COVID-19 response; the office had no role in collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: Cornell’s response to COVID-19 throughout the Fall 2021 semester was possible due to the contributions of many: Tompkins County Health Department for leadership in outbreak response, case investigation, and case support (Frank Kruppa, MPH, and Claire Espey, MPH, Rachel Buckwalter, BSN, Celeste Rakovich, RN, Shuai Yuan, MPH, Samantha Hillson, MPH, Deidre Gallow, BS); Cayuga Health System for codeveloping and managing a comprehensive polymerase chain reaction testing program in Tompkins County and collaborating to develop the Cornell COVID-19 Testing Laboratory (Martin Stallone, MD, Rob Lawlis, MEng, Elizabeth Plocharczyk, MD, Tracy Gates, MBA, Casey Frederici, Tevin R. Smith, BS); Cornell COVID-19 Response Team + Infection Working Group for developing and implementing policy to prevent and manage COVID-19 on campus (Allan Bishop, BA, and Lisa Nishii, PhD, Kristin Hopkins, BS, Shannon Osburn, John D. Clarke, MD, Tim Fitzpatrick, MS, Jada Hamilton, MD, Mary Opperman, MS, Joshua E. Turse, PhD, Isaac Weisfuse, MD, Cecelia Earls, PhD); Cornell COVID-19 Testing Lab for collecting and processing more than 408 000 samples from the Cornell community from August 23 to December 31 (Kim Potter, MBA, Rahim Rustamov, BS, Melissa Aprea, BS, Brittany D. Cronk, MS, Melissa Laverack, BS, Roopa Venugopalan, MS, Rebecca Tallmadge, PhD, and all of the testing and sampling team); Cornell COVID-19 Data + Modeling Team for facilitating and ensuring robust data collection and analysis to inform action (Marin Clarkberg, PhD, David Shmoys, PhD, and Bonnie Akhavan, BS, Jefferson Busche, MS, Josh Brockner, BS, Massey Cashore, BM, Alyf Janmohamed, BES, Brian Liu, Henry Robbins, BS, Samuel Tan, Xiangyu Zhang, Yujia Zhang); Cornell Pandemic Response Officers + Data Team for contacting and investigating more than 3000 COVID-19 cases on campus, highlighting a changing context, and helping to mitigate transmission (Donna Leong, MPH, MCP, Jefferson Busche, MS, Josh Brockner, BS, and Gina George, MPH, Jaylen C. Perkins, MPH, Marla Colino, MPH, Carolyn Voigt, BS, Parshad Mehta, BDS, Sabine Jamal, MD, Henry Robbins, BS, Ria Padshah, BS, Krista Ochoa, BS, Somya Pandey, MPH, Aaron C. Malkowski, BS, Sagarika Vemprala, BDS, Gabriella Davies Thoppil, MBBS, Halee Calabrese, BS, Byron Song, BS, Ahmad Avery, MPH, Emily Grace, MPH, Christina Shupe, BS, Keane Leitch, MPH, Ellen Reilley, MS, Liz Flint, BS); Cornell COVID-19 Support Center Team for supporting students with COVID-19 in isolating safely, and having their health and safety needs met (Leslie Meyerhoff, PhD, and Paige Hunt, BA, Anton Ochoa, BA, Wendy Franzese, BS, Cortney Utter, AA, Jeanette Mancusi, MS, Cat Holmes, MS, Kathleen M. Snyder, BA, Charmaine Robinson, Robert Kilts, AAS, Debra Walls, AAS, Kris Kaplan, BS, Erin Sill, BS, Tony Lombardo); Cornell Health COVID-19 Team for managing the initial COVID-19 surge, for training so many more support staff, and for continuing to manage students’ health needs (Bridget Flanagan, RN, and Alicia Steele, AAS, Tracy Sangprakarn, RN, Emilee Frazier, BSN).