Statistical analysis
Descriptive analyses were performed for all variables. Age was categorized in 6 age groups according to the degree of school. In Italy, children less than three months old do not attend any type of school, children from 3 months to 2 years old attend the day nursery school, children from 3 to 5 years old attend kindergarten school, children between 6 and 10 years old attend primary school, children from 11 to 13 years old attend junior secondary school and children from 14 to 19 years old attend secondary school.
To further describe the activity of the HS, descriptive statistics of the variables were stratified by setting and chi-squared tests and adjusted residuals (Kruskall Wallis test where appropriate) were calculated.
Multivariable logistic regression models were carried out to understand if children accessing the HS were more likely to be positive compared with children accessing the other settings.
SPSS statistics (v27) was used and a two-tailed p-value < 0.05 was considered significant. Missing values were excluded.