Data analysis
REGRESSION, INTERACTION
We performed descriptive analyses on socio-educational characteristics by sex and on HPV vaccine knowledge and attitude items between subgroups according to socio-educational and mitigation variables. We used chi squared tests for differences between subgroups.For the first analysis on determinants of HPV vaccine awareness (binary), vaccine status (binary) and vaccination intention (three levels: refusal, indecision, intention), we built multivariable logistic and multinomial regression models including all socio-educational variables and variables related to contact with GP, health-related knowledge, behaviour and aptitudes and social influence. For each outcome, we included in the final multivariable model only variables associated in bivariable models at p value < 0.2.For the main objective of exploring social inequalities, we analysed, for each outcome, a model including only socio-educational variables (grade level, sex, parental education, language, deprivation level). We then explored mitigation including interaction terms between socio-educational determinants (parental education, language, deprivation level) and hypothetical mitigation variables (health-related knowledge and recent GP visit). Interaction terms with p < 0.05 were interpreted as mitigation, and in this case, the effects of determinants were represented stratifying for the mitigation factor.Statistical significance was defined as p value < 0.05. Data analyses were performed on Stata Version 17 (StataCorp, the United States).