Grandahl 2016.

Methods	Cluster randomised trial conducted in Sweden
Participants	Participants: 16‐year old girls and boys Number per group: 390 students from 60 classes in intervention group and 351 students from 53 classes in a control group. Total number enrolled: 741 adolescents Study population: Swedish upper secondary school adolescents aged 16–19 years
Interventions	Intervention: face‐to‐face health education Description: face‐to‐face structured information about HPV, including cancer risks and HPV prevention, by propagating condom use and HPV vaccination. Duration: 30 minutes Comparison: usual practice Description of comparison: general information, including sexual health Vaccine target: HPV vaccine Disease targeted: cervical cancer Number of doses: not specified
Outcomes	HPV vaccine uptake
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was performed in 2 steps. First, in order to avoid contamination, the schools were randomised into either the intervention group or the control group. Second, 113 school classes within these schools were randomly selected to be included in the study.
Allocation concealment (selection bias)	Low risk	Schools were randomly drawn by administrative personnel not involved in the project.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The outcome is an objective measure.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Research assistant who recorded the data from the participants did not possess this knowledge.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up.
Selective reporting (reporting bias)	Low risk	Due to the self‐reported questionnaires, there was a risk of participants' over‐reporting or under‐reporting or having recall bias; however, we consider this risk to be small in this study.
Other bias	Low risk	No evidence of other biases.