Addressing HPV Vaccine Hesitancy by Co-Designing a Digital Health Intervention

Primary outcomes

1. Feasibility of implementation: Acceptability, appropriateness and feasibility of implementation

   Time frame: Shortly after the intervention period (i.e., 'end of treatment') at 7 months.

   Measured using Weiner et al.'s implementation outcomes questionnaire (administered to school nurses in participating schools). The questionnaire consists of 12 statements, with four items each assessing the Acceptability of Intervention Measure (AIM), the Intervention Appropriateness Measure (IAM), and the Feasibility of Intervention Measure (FIM).

   Respondents rate their level of agreement with each statement using a five-point Likert scale, ranging from "completely disagree" to "completely agree." Responses are coded numerically from 1 to 5, with higher scores indicating stronger agreement. The 12 scores are summed to produce a total scale score ranging from 12 to 60, with higher scores reflecting more positive perceptions of the platform across the three implementation domains.

2. Feasibility of implementation: Acceptability, appropriateness and feasibility of implementation

   Time frame: Shortly after the intervention period (i.e., 'end of treatment') at 7 months.

   Qualitative data will be collected through semi-structured interviews with school nurses in participating schools. An interview guide developed guided by the Consolidated Framework for Implementation Research (CFIR) will be used to ensure consistency while allowing flexibility to explore individual experiences in depth. The guide includes open-ended questions designed to capture perceptions (see outcome measure 5) and questions related to implementation, e.g., 'How did you experience implementing HPV-Kompassen alongside the regular school health services program?' and 'How well did HPV-Kompassen fit with how schools provide information about HPV vaccination?'.

3. Acceptability of intervention: Intervention delivery strategy

   Time frame: Throughout the intervention period (i.e., months 0-7).

   Defined as proportion of adolescents and caregivers that access platform at least once, measured through platform usage metrics.

4. Acceptability of intervention: Usability of intervention

   Time frame: Immediately after the intervention period (i.e., 'end of treatment') at 7 months.

   Usability is measured quantitatively using the Swedish version of the System Usability Scale (SUS). The SUS consists of 10 items assessing perceived usability across key dimensions such as complexity, ease of use, and confidence in using the system. Participants (school nurses, adolescents and caregivers) indicate their agreement with each item on a five-point Likert scale ranging from "strongly disagree" to "strongly agree." Responses are scored according to standard SUS procedures, resulting in a total score ranging from 0 to 100, with higher scores indicating better perceived usability.

5. Acceptability of intervention: Perceptions of intervention

   Time frame: Shortly after the intervention period (i.e., 'end of treatment') at 7 months.

   Qualitative data will be collected through semi-structured interviews with participants (school nurses, adolescents and caregivers), focusing on their perceptions of the intervention. An interview guide is used to ensure coverage of key domains while allowing flexibility to explore individual experiences in depth. The guide includes open-ended questions assessing implementation (see outcome measure 2) and perceptions of the intervention, such as "Can you briefly describe your experience of using HPV-Kompassen?" and "Did the information seem credible to you?".

6. Acceptability of intervention: Intervention engagement

   Time frame: Throughout the intervention period (i.e., months 0-7).

   Defined as proportion of adolescents and caregivers that actively engage with the platform least once (e.g., visit different modules), measured through platform usage metrics.

7. Acceptability of intervention: Intervention engagement

   Time frame: End of intervention period (i.e., 'end of treatment') at 7 months.

   Qualitative data collection using semi-structured interviews. These interviews aim to understand how, why, and to what extent participants engaged with the platform in practice. Participants (school nurses, adolescents and caregivers) are asked open-ended questions such as "Why did you choose to use the platform?" and "Why did you not use the platform, or use it less than expected?" Additional questions explore when and how the platform was accessed, which features were used, and what factors influenced engagement (e.g., time constraints, relevance of content, or integration with existing workflows).

8. Feasibility of trial protocol: Feasibility of recruitment

   Time frame: From start of school enrollment (i.e., pre-intervention) and throughout the intervention period (i.e., months 0-7).

   Measured through study notes, assessing two indicators: proportion of schools that consent to participate and proportion of participants that consent to participate in interviews.

9. Feasibility of trial protocol: Participant retention

   Time frame: From school enrollment (i.e., 'baseline') and throughout the intervention period (i.e., months 0-7).

   Measured using study records and platform metrics, assessing two indicators: Proportion of schools retained until study end and proportion of participants using platform who complete the end line survey.

10. Feasibility of trial protocol: Feasibility of data collection methods

    Time frame: Shortly after the intervention period (i.e., 'end of treatment') at 7 months.

    Measured using study records and survey data, assessing the completeness of data.