Background and Objective:
In Italy, the COVID-19 pandemic has caused over 4.6 million cases in individuals aged between 0 and 19. This study aims to evaluate the role of vaccination against COVID-19 in order to reduce the spread of the SARS-CoV-2 virus within schools in Modena province.

Methods:
A retrospective cohort study was performed in the period 1 September-15 December 2021 among teachers and students aged 0-19 years, screened for SARS-CoV-2 infection by nasopharyngeal swab following the detection of an index case within classroom.

Results:
In the study period, 13934 subjects were tested, of which 12534 (90%) students and 1400 (10%) teachers, from 594 different classes. A total of 1373 cases were identified, 594 index cases and 779 secondary cases, respectively. In detail, 9.8% (1225 cases) of students tested were positive for SARS-CoV-2 and 10.6% (148 cases) of teachers. Out of entire population 32.7% (4562) of participants (64.9% of teachers and 29.2% of students) were vaccinated with at least one dose of the anti-SARS-CoV-2 vaccine at the test time. Among 779 secondary cases, only 7.7% (60) were vaccinated compared to 35.1% (4408) of negative tested subjects. Most of the subjects who tested positive attended primary school (50.8%) with the highest ratio of secondary cases on index cases rate (2.19), followed by middle (24%), high school (15.2%), infant (7.2%) and nursery school (2.7%).

Conclusion:
The results of this study show the differential spread of SARS-CoV-2 within various age groups and indicate that the vaccination, available in the study period only for the population aged ≥12, may have mitigated virus spread in middle and high schools. Conversely, infant and nursery schools seemed to benefit from organization in small classes.