Background and Objective:
During the SARS-CoV-2 testing program offered through the RT-PCR test by Sapienza University of Rome, we conducted a test-negative nested case-control study between September 2021 and February 2022 to identify risk factors for acquiring SARS-CoV-2 infection among university students.

Methods:
Each positive student (case) was matched with two negative students (controls), randomly selected from individuals who tested on the same day. Participants underwent a 10-minute structured interview about exposure to modifiable and non-modifiable risk factors for acquiring SARS-CoV-2 in two weeks before testing. Multivariable conditional logistic regression analyses were performed. Adjusted odds ratio (aOR) and 95% CI were calculated. A second model was restricted to participants who did not report attending campus in the two weeks before testing.

Results:
Out of 8.730 tests for SARS-CoV-2, 122 of 173 cases were included in the study (response rate: 70.5%). A total of 366 students took part in the analysis. Most students were female (73.2%), with a mean age of 23.3±3.6 years, and vaccinated for SARS-CoV-2 (97.8%). At the multivariable analysis, significant associations were found for being a case and having had a contact with COVID-19 positive person or with influenza like (ILI) symptoms (aOR: 6.51, 95%CI 3.48-12.18), attending clubs (aOR: 4.07, 95%CI:1.52-10.90), and having only the primary vaccine cycle (aOR: 2.94, 95%CI 1.24-6.96). Instead, attending lectures at the campus (aOR: 0.34 95%CI 0.15-0.77) was a negative predictor. No association was found with other predictors. The second model showed that exposure to a COVID-19 case or someone with ILI symptoms increased the likelihood of SARS-CoV-2 infection, while being female seemed to be less associated with acquiring the infection.

Conclusions:
The results highlight how students who attend lectures in-person adhering to non-pharmacological preventive measures seem less exposed to SARS-CoV-2 infection. This finding suggests that the university environment appears to be safe.