Mantzari 2015.

Methods	Parallel‐group randomised controlled trial conducted in the UK
Participants	Participants: girls aged 16–18 years Number per group: 500 girls had not yet received an invitation to attend the vaccination programmes (first‐time invitees), and 500 girls had previously received an invitation to get vaccinated, but had failed to attend the first vaccination appointment (previous non‐attenders). Total number enrolled: 1000 girls Study population: all girls lived in Birmingham, UK, and were registered with general practitioners; were eligible to be vaccinated; and had not been vaccinated against HPV before.
Interventions	Intervention: financial incentive with standard practice in combination with reminder text messages Description: participants received invitation letters addressed to them and inviting them to attend first HPV vaccination session. The letters included the date, time, and venue of their allocated vaccination appointment. In addition to the invitation letters, all participants were sent a standard leaflet containing information about HPV and the HPV vaccine. Participants in the intervention groups received an invitation letter with an enclosed offer of Love2Shop vouchers worth GBP 45 upon completion of 3 HPV vaccination doses. Duration: 6 months Comparison: standard practice with no incentives and no reminder system Description of comparison: letters, addressed to participants, inviting them to attend their first HPV vaccination session. In addition, the participants were sent a leaflet containing information about HPV and the HPV vaccine. Vaccine target: HPV vaccines Disease targeted: cervical cancer, genital wart Number of doses: 1‐3 doses
Outcomes	HPV vaccine uptake
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random sequence generation done using the RAND function in Excel.
Allocation concealment (selection bias)	Low risk	Participants allocated to the intervention and control group using the RAND function in Excel.
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	Vaccinations administered by nurses working with Heart of Birmingham Primary Care Trust.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No lost to follow‐up.
Selective reporting (reporting bias)	Low risk	No evidence of selective reporting.
Other bias	Low risk	No evidence of other biases.