Participant characteristics
Given constraints during the COVID-19 pandemic, only 61 middle schools with 12,833 students in third and fourth grades participated in the survey. While no information on the number of school classes was collected, we estimated that baseline questionnaires were administered in 70% of classes. More details can be seen in In total, 7,632 persons opened the questionnaire, with 7,580 accepting participation and 6,992 leaving valid responses, or 54.5% (6,992/12,833) of the eligible students. There were 3,564 females and 3,428 males responding, approximately equally distributed over the two school grade levels and with similar socio-educational characteristics. More information can be seen in Overall, 4,051 (57.9%) participants had heard about the HPV vaccine (75.9% of females, 51.6% of males) and 421 (6.0%) were not sure. More information can be seen in 