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# Process evaluation of a school-based vaccination intervention to improve HPV vaccine coverage: A mixed-method study embedded in the French PrevHPV cluster randomized controlled trial

Aurélie Bocquier<sup>a, *, 1</sup>, Simon Cadoret<sup>b, 1</sup>, Estelle Fall<sup>c</sup>, Stéphanie Bonnay<sup>a</sup>, Anne-Sophie LeDuc-Banaszuk<sup>d</sup>, Marion Branchereau<sup>d, e</sup>, Aurélie Gauchet<sup>f</sup>, Sébastien Bruel<sup>g, h</sup>, Amandine Gagneux-Brunon<sup>i, j</sup>, Bruno Giraudeau<sup>k, l</sup>, Morgane Michel<sup>m, n</sup>, Judith E. Mueller<sup>o, p</sup>, Benjamin Lefèvre<sup>a, b, 2</sup>, Nathalie Thilly<sup>a, q, 2</sup>, on behalf of the PrevHPV Study Group

## ARTICLE INFO

### Keywords:

Human papillomavirus

Vaccination

School-based immunization program

Mixed-method study

Implementation

Acceptability

## ABSTRACT

**Background:** Human papillomavirus vaccine coverage (HPV VC) remains suboptimal in many countries. French authorities launched the PrevHPV research program, which included a cluster randomized controlled trial (cRCT) to evaluate the effectiveness of an 'at-school vaccination' intervention. Within this trial, we conducted a process evaluation of this intervention, specifically analyzing (i) its implementation, (ii) its mechanisms of impact, and (iii) the contextual factors influencing implementation (facilitators/barriers).

**Method:** We conducted a mixed-method study embedded in the PrevHPV cRCT (April 2021–April 2022). 'At-school vaccination' consisted of vaccination day(s) on school premises where mobile vaccination teams (MVTs) initiated HPV vaccination free of charge for eligible adolescents (i.e., non-vaccinated adolescents aged 11+). Quantitative data were collected through activity reports and self-administered questionnaires of adolescents and school staff. Qualitative data collected through six focus groups with school staff and MVTs were analyzed using thematic analysis.

**Results:** Of the 31 schools (14,772 adolescents) randomized to implement 'at-school vaccination', 12 (39 %) dropped out. Among the participating schools, analysis of implementation showed that 17 % of adolescents returned valid consent forms, of whom 89 % initiated vaccination. MVTs played a central role in implementing vaccination day(s), supported by several school staff (e.g., school nurses, education assistants). Regarding

<footnote><sup>a</sup> Université de Lorraine, Inserm, INSPIIRE, F-54000 Nancy, France</footnote>

<footnote><sup>b</sup> Université de Lorraine, CHRU-Nancy, Service des Maladies Infectieuses et Tropicales, F-54000 Nancy, France</footnote>

<footnote><sup>c</sup> Université de Lorraine, Inserm, INSPIIRE, F-57000 Metz, France</footnote>

<footnote><sup>d</sup> Centre Régional de Coordination des Dépistages des cancers-Pays de la Loire, Angers, France</footnote>

<footnote><sup>e</sup> Institut de Cancérologie de l'Ouest (ICO), F-49055 Angers, France</footnote>

<footnote><sup>f</sup> Univ. Savoie Mont Blanc, Univ. Grenoble Alpes, LIP/PC2S, 38000 Grenoble, France</footnote>

<footnote><sup>g</sup> Department of General Practice, Jacques Lisfranc Faculty of Medicine, Saint-Etienne-Lyon University, Saint-Etienne, France</footnote>

<footnote><sup>h</sup> Health, Systemic, Process, Research Unit 4129, University Claude Bernard Lyon 1, University of Lyon, Lyon, France</footnote>

<footnote><sup>i</sup> Centre International de Recherche en Infectiologie, Team GIMAP, INSERM, Université Jean Monnet, Saint-Etienne, France</footnote>

<footnote><sup>j</sup> Service d'Infectiologie, CHU de Saint-Etienne, Saint-Etienne, France</footnote>

<footnote><sup>k</sup> Université de Tours, Université de Nantes, SPHERE U1246, Inserm, F-37044 Tours, France</footnote>

<footnote><sup>l</sup> CIC 1415, Université de Tours, Inserm, CHRU de Tours, F-37044 Tours, France</footnote>

<footnote><sup>m</sup> Université Paris Cité, ECEVE, UMR 1123, Inserm, F-75010 Paris, France</footnote>

<footnote><sup>n</sup> Assistance Publique-Hôpitaux de Paris, Hôpital Robert Debré, Unité d'épidémiologie clinique, F-75019 Paris, France</footnote>

<footnote><sup>o</sup> Institut Pasteur, Université Paris Cité, Unité d'Epidémiologie des Maladies Emergentes, F-75015 Paris, France</footnote>

<footnote><sup>p</sup> Université de Rennes, EHESP, CNRS, Inserm, Arènes – UMR 6051, RSMS (Recherche sur les Services et Management en Santé) – U 1309, F-35000 Rennes, France</footnote>

<footnote><sup>q</sup> Université de Lorraine, CHRU-Nancy, Département Méthodologie, Promotion, Investigation, F-54000 Nancy, France</footnote>

<footnote>* Corresponding author at: UMR 1319 INSPIIRE, Campus Brabois santé, Faculté de médecine, maïeutique et métiers de la santé, 9 avenue de la forêt de Haye - BP 20199, 54505 Vandœuvre-lès-Nancy Cedex, France.</footnote>

<footnote>E-mail address: aurelie.bocquier@univ-lorraine.fr (A. Bocquier).</footnote>

<footnote n="1">¹ Co-first authors, both authors contributed equally.</footnote>

<footnote n="2">² Co-last authors, both authors contributed equally.</footnote>
mechanisms of impacts, satisfaction with the vaccination days was high among adolescents and school staff. The intervention generated both positive and negative group effects among adolescents. Contextual factors that facilitated implementation included the preparation of a list of adolescents to be vaccinated and the availability and motivation of school staff. The main barriers related to the management of consent forms and missing health records.

**Conclusion:** We formulated recommendations for implementing at-school vaccination, which may be particularly helpful for the French school HPV vaccination campaigns that were scaled up nationally in 2023. We also discussed potential macro-level improvement strategies, involving modifications to the legislative framework.

**Trial registration:** Clinicaltrials.gov, NCT 04945655. Registered 30 June 2021, https://clinicaltrials.gov/study/NC/T04945655.

# 1. Introduction

Human papillomavirus (HPV) infection is the most common sexually transmitted viral infection and causes major public health issues [1]. Vaccination is the most effective primary prevention strategy for HPV [2]. Since the first HPV vaccine was marketed and introduced to the vaccination schedules of most high-income countries (HICs) in 2006–2007, vaccine coverage (VC) has remained suboptimal, falling short of the target set in the 2020 WHO Global Strategy to Accelerate the Elimination of Cervical Cancer as a Public Health Problem (i.e., 90 % coverage among girls by age 15 by 2030) [3–6]. This is particularly the case in France, where HPV VC has been among the lowest in HICs [3–5]. Initially recommended for girls only, HPV vaccination has been recommended in France for all adolescents aged 11–14 years since 2021, with catch-up vaccination possible up to age 19 [7]. At the time the present study was launched, the vast majority of HPV vaccines were prescribed and administered in private general practices [8]. No nationwide school-based vaccination program had been implemented since the hepatitis B program was halted by the Ministry of Health in 1998, following reports of neurological events [9].

High-quality evidence from previous cluster randomized controlled trials (cRCTs) has shown that at-school vaccination was effective in increasing influenza VC [10,11]. To our knowledge, no such study has been conducted specifically on HPV vaccination, but observational and quasi-experimental studies suggest that at-school vaccination can improve HPV VC [4,12–15]. Countries that have implemented routine school-based vaccination programs (e.g., Norway, UK, Canada, Australia) generally achieve higher HPV VC than those relying solely on private practices or public community health clinics [4,5], although disparities may still exist within countries [16–18]. Several factors may influence HPV vaccine uptake in the context of at-school vaccination: (i) individual and interpersonal factors (e.g., adolescents', parents', school staff's knowledge and attitudes toward HPV vaccination, as well as fear of needles, pain, and anxiety), (ii) organizational factors (e.g., the process of distributing and collecting consent forms, communication tools, and allocated resources), and (iii) public policies and communities factors (e.g., misinformation on vaccination from the Internet and social media, and vaccine supply availability at the school) [19–21].

In this context, in 2018, the French authorities launched a national research program (called PrevHPV) to improve HPV vaccine acceptability and VC among adolescents. This program included a cRCT designed to evaluate the effectiveness of an ‘at-school vaccination’ intervention [22]. Primary analyses, conducted without accounting for the dose of intervention received (i.e., the degree of implementation of the intervention), showed that ‘at-school vaccination’ significantly increased VC at two months (effect size: 5.50 percentage points (pp), *p* < 0.001) [23]. The effect size doubled when the dose of intervention was considered (11.25 pp., *p* < 0.001) [24], indicating that there was a room for improvement in how the intervention was implemented. An in-depth analysis of the implementation of the intervention would therefore be useful to identify ways to optimize it before potential scale-up and could also inform countries considering the widespread introduction of HPV at-school vaccination [25]. For this purpose, process evaluations, which aim at understanding how and why an intervention ‘worked’ (or did

not), are highly valuable [20], as emphasized by the Medical Research Council (MRC) [26].

The aim of the present study was to conduct a process evaluation of the ‘at-school vaccination’ intervention within the PrevHPV cRCT. Specific aims were to examine (i) implementation (i.e., what was delivered and how), (ii) mechanisms of impact and (iii) the contextual factors that influenced implementation (i.e., facilitators and barriers). Ultimately, the goal was to develop recommendations which could inform stakeholders and policymakers.

# 2. Materials and methods

## 2.1. Study design

This study used a mixed methods design based on quantitative and qualitative research methods and was embedded in the PrevHPV cRCT [22] (Clinicaltrials.gov, NCT04945655). Briefly, this pragmatic open-label cRCT with an incomplete factorial design was conducted in France between April 2021 and April 2022. The cluster was the municipality. Municipalities were eligible if (1) they were located in one of fourteen school districts selected to ensure diverse geographical, demographic and socioeconomic profiles; (2) there was only one middle school in the municipality; and (3) at least two-thirds of the 11- to 14-year-olds living in that municipality attended the middle school. Only municipalities whose middle school agreed to participate were included in the cRCT and were randomized into one of six groups (Fig. 1). The factorial design was incomplete because ‘at-school vaccination’ was never conducted without prior ‘education and motivation’ of parents and adolescents to allow for an informed decision making.

## 2.2. Description of the ‘at-school vaccination’ PrevHPV intervention

Details about the development and content of the ‘at-school vaccination’ intervention (Table 1) and the preceding ‘education and motivation’ one were previously described [27].

Briefly, ‘at-school vaccination’ consisted of one or several vaccination day(s) on the school premises (Groups 1 and 3 – Fig. 1) during which health professionals from local vaccination centers (‘mobile vaccination team’, MVT) initiated HPV vaccination (first dose) in accordance with safety and hygiene standards. Vaccination with the nonavalent HPV vaccine was offered free of charge without a prior medical prescription. Before the vaccination day(s), school staff provided parents with consent forms and then collected the forms. On the vaccination day, the MVT checked each adolescent’s eligibility for vaccination before administering the vaccine: i.e., according to their health records, were ≥11 years old (middle school pupils in France are typically aged 11–15), had not previously received the HPV vaccine, had no contraindication to vaccination, and parents provided written consent. In France, every child receives a personal health record at birth; this document is used to record key health events and all vaccinations administered. To date, it remains the official means of verifying adolescents’ vaccination status.

To improve implementation, we used the following strategies, which were based on the Expert Recommendations for Implementing Change
(ERIC) project categories [28,29]: identify and prepare a 'champion' (i.e., a school project leader was identified in each school and was provided with tools and support to promote the implementation of the intervention in his or her school); provide interactive assistance/facilitation (i.e., for each school, an external facilitator from the research teams provided support to his or her schools throughout implementation); promote adaptability (i.e., adaptation of the intervention to the constraints of each school was allowed); and develop/distribute educational material (i.e., stakeholders were provided with guidelines and tools to help them deliver the intervention).

## 2.3. Data collection

Using the MRC process evaluation framework [26] as a guide, we collected quantitative and qualitative data on implementation (the structures, resources and processes through which delivery was achieved, and the quantity and quality of what was delivered), mechanisms of impact (specifically, how participants responded to and interacted with the intervention, e.g., acceptability and satisfaction), and contextual factors that influenced implementation (facilitators and barriers that influenced the delivery and functioning of the intervention).

### 2.3.1. Quantitative data

Data on implementation and contextual factors (facilitators and barriers) were collected through paper standardized activity reports

completed by external facilitators from the research teams who attended the vaccination days. For each vaccination day, standardized activity reports included data on the MVT (e.g., number of professionals and their professions, arrival/departure time), HPV vaccine injections (e.g., number of injections planned, administered, and not administered and reasons for non-administration), and logistical aspects (e.g., which professionals were involved, at which stage, how many rooms and what equipment was used). After the vaccination day(s) in each school, external facilitators recorded the facilitators of and barriers to the preparation and implementation of 'at-school vaccination' in activity reports, in collaboration with school project leaders, using a standardized form with multiple choice closed-ended questions and with an additional 'Other' category.

Data on the mechanisms of impact (acceptability and satisfaction) were collected through self-administered questionnaires from vaccinated adolescents (Supplementary Document S1) and school staff (Supplementary Document S2). Immediately after vaccine administration, the adolescents completed a paper questionnaire that collected data on their main source of information about HPV, how the decision to receive vaccination was made, a priori concerns about the injection, their perceived level of pain, whether they asked the health professionals of the MVT any questions (and, if so, their satisfaction with the answers), and their overall satisfaction with the vaccination day(s) at school. For school staff, an online questionnaire was sent by the school project leader to all school staff, the week after the vaccination day(s) to

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Flowchart of the municipality selection and group allocation of the PrevHPV cluster randomized controlled trial. GP: general practitioner. Mean/median size: mean/median number of inhabitants aged 11 to 14 (census data).</figcaption></figure>
<caption>**Table 1**</caption>

Steps of the 'at-school vaccination' PrevHPV intervention,ª as planned in the protocol.

<table><caption>**Table 1 (continued)**</caption><thead><tr><th>Period/date</th><th>Step</th></tr></thead><tbody><tr><td>April–July 2021</td><td><ul><li>The research team informed the national, regional and local levels of national education and contacted the heads of eligible schools to invite them to participate.</li><li>The head of the school decided to participate and assigned a school project leader.</li></ul></td></tr><tr><td>September 2021</td><td><ul><li>The research team provided the school project leader (± head of school) with information about the intervention via an online meeting.</li><li>The research team contacted the professionals from the MVT and provided them a 'mobile vaccination team handbook'.</li><li>The school project leader and the MVT prescheduled vaccination days.</li></ul></td></tr><tr><td>January 2022</td><td><ul><li>The school project leader informed parents about the vaccination day by email and provided all adolescents with paper consent formsᵇ for their parents.</li><li>The school project leader displayed postersᵇ on school promises to inform adolescents about the vaccination day.</li></ul></td></tr><tr><td>February 2022</td><td><ul><li>Parents filled out consent forms.</li><li>The school project leader collected and verified consent forms.</li></ul></td></tr><tr><td>March 2022</td><td><ul><li>The school project leader established the list of adolescents to be vaccinated.</li><li>The MVT and the school project leader defined the number of half-days/full vaccination days needed, and were encouraged to talk together to organize the practical aspects of these days.</li></ul></td></tr><tr><td>March 2022<br>≈2 weeks before the vaccination day</td><td><ul><li>The school project leader reserved the room(s) that would be made available to the health professionals from the MVT (4 requested in the protocol).</li><li>The school project leader planned the order in which the adolescents would be vaccinated, and organized how they would go to the vaccination room/return to class.</li><li>The MVT prepared the materials needed for the vaccination day (e.g., vaccinesᵇ, vaccine transportation, prescription booklet).</li></ul></td></tr><tr><td>March–April 2022<br>Vaccination day(s)</td><td><ul><li><strong>Before vaccine administration:</strong><ul><li>The school project leader welcomed the MVT and the external facilitator from the research team.</li><li>The school project leader provided the MVT with the list of adolescents to be vaccinated and parental consent forms.</li><li>Adolescents arrived in the vaccination room with their health records, according to the organization planned by the school project leader.</li><li>The physician from the MVT checked the eligibility of each adolescent (e.g., absence of contraindications to vaccination, parental consent form).</li><li>For eligible adolescentsᶜ, the MVT administered the first dose of the nonavalent vaccine GARDASIL 9®,<ul><li><strong>After vaccine administration:</strong><ul><li>The physician from the MVT completed/signed the adolescent's health record and postvaccination documents to inform his or her parents, family physician and pharmacist and prescribed the second injection.</li><li>Vaccinated adolescents remained under observation for 15–20 min in the designated room before returning to class with their documents.</li></ul></li></ul></li></ul></td></tr></tbody></table>

<table><thead><tr><th>Period/date</th><th>Step</th></tr></thead><tbody><tr><td></td><td><ul><li>The MVT recorded data in the database, archived consent forms, and disposed of infectious health care waste from the school.</li></ul></td></tr></tbody></table>

MVT: mobile vaccination team.

ª As part of the PrevHPV trial, at-school vaccination was not performed without prior education and motivation of the parents and adolescents to allow for an informed decision. Thus, in December 2021, all parents were invited by the school to participate in a web conference on HPV infection and vaccination delivered by two experts. In January and February 2022, adolescents from the 8th- and 9th-grade classes (13–15 years old) attended two two-hour educational group sessions on these topics during school hours.

ᵇ Provided by the research team.

ᶜ The health professionals from the MVT provided noneligible adolescents with a nonvaccination letter for parents that explained why their child was not vaccinated.

collect data on whether the vaccination day(s) had an effect on their routine school activities and their overall satisfaction with these day(s).

### 2.3.2. Qualitative data

Six focus groups were conducted online using Microsoft Teams in June 2022; four with school staff and two with professionals from the MVTs involved in the implementation of 'at-school vaccination'. They received an email invitation from the research teams to participate in an online focus group (expected duration: 1 h30) and an information sheet that stated that participants would be offered a 50¢ shopping voucher. Interested people were asked to contact the research teams by email so that they could receive the invitation to the focus groups. We aimed to include approximately 6 participants per focus group [30]. After oral consent was received, all focus groups were recorded and transcribed.

Each focus group was conducted by two members of the research teams (A.B., A.G., J.A., and/or S.B.) and followed an interview guide composed of open-ended questions. The interview guide was developed through informal consensus by members of the research teams based on their expertise in qualitative research and guidance for the process evaluation of complex interventions [26]. For school staff, the interview guide (Supplementary Document S3) explored how the at-school vaccination was implemented, the barriers and facilitators encountered, and their perceptions of the impact on and satisfaction of adolescents and parents. For the MVTs, the interview guide (Supplementary Document S4) explored how the vaccination days were prepared and implemented, the documents required, and the barriers and facilitators encountered.

## 2.4. Data analysis

The quantitative data collected in paper format were recorded by members of the research teams via an electronic case report form. One team member (S.B.) verified the consistency and accuracy of the entire dataset. Descriptive statistics were used to describe the implementation of 'at-school vaccination', its acceptability, satisfaction with the intervention, as well as facilitators and barriers. Quantitative variables are presented as means and standard deviations, and categorical variables are presented as numbers and percentages. The two questions on adolescents' main sources of information about HPV were recoded; a source of information was considered used if it was selected in either of the two questions. All analyses were performed with Microsoft Excel®.

For the qualitative data, transcripts of the focus groups were analyzed using thematic analysis approach [31]. Each transcript of the focus groups was read several times to become familiar with the participants' responses. Informative statements were extracted from the transcripts into units of meaning, and categorized into themes and subthemes using an inductive method. An analysis grid was developed in Microsoft Excel by a medical student specialized in infectious diseases
(S.C.) and validated by a senior health psychologist (E.F.) and two members of the research teams (A.B., S.B.). Each theme and subtheme of this grid was discussed and iteratively refined until consensus was reached. Each focus group was then coded according to the grid. In a second step, these themes and subthemes were mapped deductively by A.B. onto the three MRC process evaluation dimensions (implementation, mechanisms of impact and contextual factors) to facilitate the integration of findings from qualitative and quantitative data in a mixed-method approach.

## 2.5. Ethics

This study was granted approval by the French Ethics Committee ‘Comité de Protection des Personnes—CPP Sud-Est VI’ on 22 December 2020 (ID-RCB: 2020-A02031–38). All participants were informed of their rights, particularly the right not to participate or to withdraw from the collection of their data.

# 3. Results

## 3.1. Participants

Of the 31 schools (14,772 adolescents), from 31 different municipalities, that agreed to participate in July 2021 and were randomized to the ‘at-school vaccination’ groups (1 and 3), 12 (39 %) dropped out between September 2021 and March 2022 and did not implement any action related to this component (the main reasons included a complicated period due to the COVID-19 pandemic, lack of time and/or resources, and staff turnover). Among the 19/31 (61 %) schools that continued (8494 adolescents), external facilitators from the research teams completed standardized activity reports for all vaccination days organized. A total of 1212/1256 (97 %; 57 %–100 % by schools) vaccinated adolescents completed the postvaccination paper questionnaire and 65 staff from 16 different schools completed the online questionnaire.

A total of 26 professionals participated in the six focus groups (17 school staff from 11 different schools and nine professionals from six different MVTs). Their characteristics are presented in Table 2. Four main themes emerged from the thematic analysis (human resources, administrative elements, practical organization, and contextual and social factors) and are presented below, as well as in Table 3, within each dimension of process evaluation. Quotes are presented in Table 4.

## 3.2. Implementation

### 3.2.1. Quantitative data

Among the 19 participating schools, project leaders were most frequently school nurses (12/19 schools, 63 %) or head/assistant head of school (5/19 schools, 26 %). In 17/19 schools (89 %), they provided parents of pupils in grades 6 to 9 with consent forms, as planned in the protocol. In two schools (11 %), only 8th- and 9th-grade pupils were targeted, due to a lack of school staff. Among the 8257 adolescents invited to receive HPV vaccination at school in the 19 participating schools, 1409 (17 %) returned valid consent forms (i.e., no missing data, signed by both parents). The total number of valid consent forms led school project leaders and MVTs to schedule a total of 28 vaccination days. Eleven (58 %) schools scheduled one vaccination day, 7 (37 %) scheduled two days, and one (5 %) scheduled three days.

The vaccination days were organized in one to five rooms depending on the school (5/19, 26 % used four rooms as planned in the protocol; 12/19, 63 % used fewer than four rooms). These rooms were most frequently infirmaries (in 9/19 schools, 47 %), rooms attached to the infirmary (e.g., adjoining corridors, waiting rooms, offices) (6/19, 32 %), and classrooms (6/19, 32 %). Some rooms were separated by screens for privacy.

On vaccination days, the MVT spent an average of 5 h 52 (±1 h 35)

<table><caption>**Table 2**

Characteristics of the participants in the focus groups (n = 26).</caption><thead><tr><th>Participant ID</th><th>Profession</th><th>Sex</th><th>School/mobile vaccination team ID</th><th>School size (no. of pupils)</th></tr></thead><tbody><tr><td colspan="5">Focus group 1 (n = 3; duration: 1 h 37)</td></tr><tr><td>P1</td><td>School nurse</td><td>F</td><td>S1</td><td>[300–400]</td></tr><tr><td>P2</td><td>Chief education advisor</td><td>F</td><td>S1</td><td>[300–400]</td></tr><tr><td>P3</td><td>School nurse</td><td>F</td><td>S2</td><td>[100–200]</td></tr><tr><td colspan="5">Focus group 2 (n = 4; duration: 1 h 52)</td></tr><tr><td>P4</td><td>School nurse</td><td>F</td><td>S3</td><td>[100–200]</td></tr><tr><td>P5</td><td>School nurse</td><td>F</td><td>S4</td><td>[400–500]</td></tr><tr><td>P6</td><td>Teacher in life sciences</td><td>F</td><td>S5</td><td>[300–400]</td></tr><tr><td>P7</td><td>School nurse</td><td>F</td><td>S6</td><td>[300–400]</td></tr><tr><td colspan="5">Focus group 3 (n = 6; duration: 1 h 38)</td></tr><tr><td>P8</td><td>Head of school</td><td>F</td><td>S7</td><td>[500–600]</td></tr><tr><td>P9</td><td>Head of school</td><td>M</td><td>S8</td><td>[300–400]</td></tr><tr><td>P10</td><td>Teacher in life sciences</td><td>F</td><td>S8</td><td>[300–400]</td></tr><tr><td>P11</td><td>Head of school</td><td>M</td><td>S5</td><td>[300–400]</td></tr><tr><td>P12</td><td>Assistant head of school</td><td>F</td><td>S5</td><td>[300–400]</td></tr><tr><td>P13</td><td>Head of school</td><td>F</td><td>S9</td><td>[400–500]</td></tr><tr><td colspan="5">Focus group 4 (n = 4; duration: 1 h 19)</td></tr><tr><td>P14</td><td>Head of school</td><td>M</td><td>S10</td><td>[900–1000]</td></tr><tr><td>P15</td><td>Assistant head of school</td><td>F</td><td>S4</td><td>[400–500]</td></tr><tr><td>P16</td><td>Head of school</td><td>F</td><td>S11</td><td>[500–600]</td></tr><tr><td>P17</td><td>Assistant head of school</td><td>F</td><td>S11</td><td>[500–600]</td></tr><tr><td colspan="5">Focus group 5 (n = 4; duration: 1 h 45)</td></tr><tr><td>P18</td><td>Physician</td><td>F</td><td>MVT1</td><td>N/A</td></tr><tr><td>P19</td><td>Administrative assistant</td><td>F</td><td>MVT1</td><td>N/A</td></tr><tr><td>P20</td><td>Nurse</td><td>F</td><td>MVT2</td><td>N/A</td></tr><tr><td>P21</td><td>Administrative assistant</td><td>F</td><td>MVT3</td><td>N/A</td></tr><tr><td colspan="5">Focus group 6 (n = 5; duration: 1 h 41)</td></tr><tr><td>P22</td><td>Physician</td><td>F</td><td>MVT4</td><td>N/A</td></tr><tr><td>P23</td><td>Physician</td><td>F</td><td>MVT5</td><td>N/A</td></tr><tr><td>P24</td><td>Administrative assistant</td><td>F</td><td>MVT3</td><td>N/A</td></tr><tr><td>P25</td><td>Nurse</td><td>F</td><td>MVT4</td><td>N/A</td></tr><tr><td>P26</td><td>Physician</td><td>M</td><td>MVT6</td><td>N/A</td></tr></tbody></table>

F: female; M: male; MVT: mobile vaccination team; N/A: nonapplicable; P: participant; S: school.

on school premises. Over the 27/28 (96 %) vaccination days for which information was available, the MVT included a physician for each vaccination day, as planned in the protocol. The team also frequently included a nurse (12/27 days, 44 %), an administrative assistant (7/27, 26 %) or both (8/27, 30 %). The presence of a school nurse was reported for 15/27 (55 %) vaccination days. Adolescents were accompanied to the vaccination rooms by education staff (in 8/19 schools, 42 %), school nurses (4/19, 21 %) or both (4/19, 21 %), or went independently (2/19, 11 %). They usually returned to class on their own (16/19, 84 %) or accompanied by an education assistant (3/19, 16 %) after remaining under observation for 15–20 min, as planned.

Among the 1409 injections planned, 1256 (89 %) were performed (girls: 575; boys: 681). The most common reasons for non-injection were the absence of eligible adolescents on the vaccination day and missing health records among adolescents who were present. To address the issue of missing health records, in 8/19 (42 %) schools, the MVT and/or the school nurse called parents or family physicians to verify the
<table><caption>**Table 3**
Main results for each theme that emerged from the analysis of the focus groups.</caption><thead><tr><th rowspan="2">Theme</th><th colspan="3">Main results</th></tr><tr><th>Implementation</th><th>Mechanisms of impact</th><th>Facilitators/ Barriers</th></tr></thead><tbody><tr><td colspan="4"><strong>Theme 1. Human resources</strong></td></tr><tr><td>MVT</td><td>Composed of a physician, nurse and/or an administrative assistant. Central role on the vaccination day.</td><td>/</td><td>F. Experience in managing vaccination days.</td></tr><tr><td>Heads of schools</td><td>Made the decision to organize the vaccination days.</td><td>Informed the parents.</td><td>F. Involvement and motivation.</td></tr><tr><td>School nurses</td><td>Prepared the vaccination day; sometimes present during the vaccination day.</td><td>Informed the adolescents.</td><td>F. Motivation and presence during the vaccination day.<br>B. Limited time in school, no financial compensation.</td></tr><tr><td>Education assistants</td><td>Helped prepare the vaccination day; accompanied adolescents during the vaccination day.</td><td>/</td><td>F. Experience in managing pupils' flow.</td></tr><tr><td>External facilitators (research team)</td><td>Coordinated stakeholders from schools and MVT.</td><td>/</td><td>F. Presence during the vaccination day.</td></tr><tr><td colspan="4"><strong>Theme 2. Administrative elements</strong></td></tr><tr><td>Consent forms</td><td>Paper consent forms distributed, collected, and checked by school staff.</td><td>Valid consent forms (completed, signed by both parents) mandatory.</td><td>B. Management time-consuming for school staff; hard to understand for non-French-speaking families.</td></tr><tr><td>List of adolescents to be vaccinated</td><td>Key element to plan and organize the vaccination day.</td><td>/</td><td>/</td></tr><tr><td>Health records</td><td>Required to check for eligibility for HPV vaccine and record the vaccination.</td><td>Sometimes used to remind adolescents of other vaccines to be done.</td><td>B. Missing health records on the vaccination day.</td></tr><tr><td>Prescriptions for the second HPV vaccine injection</td><td>Provided by the MVT on the vaccination day.</td><td>To facilitate the injection of the second dose of HPV vaccine.</td><td>F. Prepared prior to the vaccination day.</td></tr><tr><td>Postvaccination documents</td><td>Provided by the MVT on the vaccination day.</td><td>To inform parents, family physicians, pharmacists.</td><td>B. Perceived as not relevant by some MVTs.</td></tr><tr><td colspan="4"><strong>Theme 3. Practical organization of vaccination day(s)</strong></td></tr><tr><td>Date selection</td><td>Chosen by agreement of schools and MVT.</td><td>/</td><td>F. Chosen in advance.</td></tr><tr><td>Geographical/ spatial organizational aspects</td><td>Distance between the school and the vaccination center as a key factor. Varying number of rooms used in practice.</td><td>/</td><td>B. Travel time for MVTs could be high (&gt;1 h). F. Adaptability of the MVT to the school premises.</td></tr><tr><td>Required and available equipment</td><td>Refrigerator and water access point required in the protocol; in practice, use of MVT coolers.</td><td>/</td><td>F. School premises well equipped. B. Internet connection required by MVT.</td></tr></tbody></table>

<table><caption>**Table 3 (continued)**</caption><thead><tr><th rowspan="2">Theme</th><th colspan="3">Main results</th></tr><tr><th>Implementation</th><th>Mechanisms of impact</th><th>Facilitators/ Barriers</th></tr></thead><tbody><tr><td>Adolescents' accompaniment to the vaccination rooms</td><td>Accompanied by education assistants or arrived independently.</td><td>/</td><td>/</td></tr><tr><td>Postinjection observation</td><td>Adolescents stayed ≈ 15 min before returning to class; physicians stayed at least 30 min after the last injection.</td><td>/</td><td>/</td></tr><tr><td colspan="4"><strong>Theme 4. Contextual and social factors</strong></td></tr><tr><td>COVID-19 pandemic</td><td>/</td><td>/</td><td>F. Provided school staff with experience in organizing vaccination days. B. Parents worried about many things other than HPV vaccination, rejected one more vaccination. B. Threats against schools.</td></tr><tr><td>Parents' reluctance about vaccination</td><td>/</td><td>/</td><td></td></tr><tr><td>Group effects</td><td>/</td><td>/</td><td>Parents and/or adolescents who were convinced of the benefits of the HPV vaccine could make those who were reluctant change their mind. On the vaccination day, vaccinated adolescents could discourage those waiting to be vaccinated.</td></tr></tbody></table>

B: barrier; F: facilitator; MVT: mobile vaccination team.

adolescents' eligibility and/or obtain a picture of the health record.

Six adverse events were recorded during 4/28 (14 %) vaccination days: vasovagal syncope after injection (four cases), nosebleed (one case), and sensory disturbance in the arm where the vaccine was injected (one case).

### 3.2.2. Qualitative data

Findings from qualitative analysis confirmed that MVTs played a central role during the vaccination day(s) (Table 3, Table 4). They brought materials and vaccines, checked the consent forms and health records, administered the vaccines, provided prescriptions for the second injection, and monitored the vaccinated adolescents afterward (physicians from the MVTs stayed at least 30 min after the last injection of the day) (quotes 1 and 2).

Some physicians from the MVTs also took the opportunity of the vaccination days to check the adolescents' vaccination status for vaccines other than HPV and reminded them about vaccines they needed.

The results highlighted the role of school staff, especially school nurses, who are health referents in schools, know adolescents well, and
<table><caption>**Table 4**
Quotes extracted from the focus groups transcripts.</caption><thead><tr><th>Quote number</th><th>Verbatim</th></tr></thead><tbody><tr><td>1</td><td>"They [the professionals from the MVT] have everything they need. They're the ones who'll come [...]. They're the ones who'll manage everything. All we [the school staff] need to do is organize the adolescents' flow." (P3)</td></tr><tr><td>2</td><td>"The pupil came back into the area where we [professionals from the MVT] were with them for those who were waiting to be vaccinated and for those who had to wait to make sure there were no problems. And we did, in fact, stay after the last child had been vaccinated [...] we felt that it was our responsibility to stay afterward" (P21).</td></tr><tr><td>3</td><td>"I [a professional from the MVT] managed the vaccination side. She [the school nurse] really managed everything else." (P25)</td></tr><tr><td>4</td><td>"The education assistants are in charge of different class levels, so they took care of handing out the envelopes [consent forms] [...] they are really used to this kind of exercise. Kids who were missing in the morning or didn't have their documents were replaced by others from the afternoon. It all went very smoothly." (P11)</td></tr><tr><td>5</td><td>"We [the school staff] organized everything well enough in advance to be able to schedule the appointments, arrange everything with the education assistants and the group rotations and let the teachers know beforehand so that they were not surprised by the absence of some adolescents." (P9)</td></tr><tr><td>6</td><td>"The time and the availability of the medical staff and my team [MVT nurses] are not extensible, especially for the medical staff. [...] We have a very large area, and we sometimes have to drive up to 2 h to get there. [...]" (P25)</td></tr><tr><td>7</td><td>"I [the head of the school] have received a lot of emails insulting me for what we did..." (P8)</td></tr><tr><td>8</td><td>"What was very marginal, for us anyway, is the very principle of the question of vaccination, [...] There was some feedback, [...] from families who were reluctant out of principle, out of conviction" (P9)</td></tr><tr><td>9</td><td>"Families discussed the issue among themselves [...] they managed to convince others. The same with adolescents – they discussed it among themselves, and adolescents whose families were reluctant campaigned at home to convince their parents of the benefits of getting vaccinated" (P17)</td></tr><tr><td>10</td><td>"We [the school staff] took them in small groups. [...] You also have to realize that the children between them [...] they're also able to get each other worked up: 'Aren't you scared?'" (P21)</td></tr><tr><td>11</td><td>"Once the child has been vaccinated, it's written in the health record. We [professionals from the MVT] don't inform the parent unless there's been a problem... But you don't get a letter saying that your child has been vaccinated since it's written in the booklet." (P18)</td></tr><tr><td>12</td><td>"You [the MVT] know roughly how many you have. So afterwards, you need to see how many you're seeing in a given time slot, whether or not it's compatible with working with a physician, a nurse, 2 nurses, 3 nurses. [...] We also kept a computer log beforehand with our administrative assistant so that we could keep track of them in the software [...] which meant we could anticipate the volume a little." (P26)</td></tr><tr><td>13</td><td>"On the first day, we [the MVT] had to make all the prescriptions on the fly... we hadn't anticipated that we'd have to redo the prescriptions... When they're prepared in advance, it's easier. We just need to fill in the surname, first name and number of doses according to the patient's age." (P26)</td></tr><tr><td>14</td><td>"First, the premises made things easier because they're new. [...] I [the school nurse] have got everything. [...] I've got the internet, I've got a phone, we've got a fridge to store the injections and a place to wash our hands." (P3)</td></tr><tr><td>15</td><td>"I [a professional from the MVT] don't see a problem if the head of the school is on board. [...] If he believes that the project has potential, he'll rally his staff; if he goes reluctantly, then it means it's failed in terms of cost-effectiveness." (P18)</td></tr><tr><td>16</td><td>"If the nurse didn't want to take part in the project, it's also because there was no financial compensation planned." (P14)</td></tr><tr><td>17</td><td>"It [managing consent] took me an insane amount of time... Having to constantly chase adolescents and send back emails. [...] And when I only had one [signature], asking whether it was because the parents didn't want to provide two or because it wasn't possible for personal reasons." (P10)</td></tr><tr><td>18</td><td>"For non-French speaking families, consent was far too complex to give, and they gave up vaccination altogether." (P14)</td></tr><tr><td>19</td><td>"The doctor called the parents. It's a lot more work. I mean, they had to be contacted, the parents, who often were at work. It was a bit complicated. It slowed down the process quite a bit." (P20)</td></tr><tr><td>20</td><td>"COVID vaccinations we [the school staff] did in the schools, so we were very well versed... It wasn't complicated at all." (P8)</td></tr><tr><td>21</td><td>"It's true that it wasn't the best of times either with COVID and vaccinations, which were already a hot topic in the schools." (P5)</td></tr></tbody></table>

MVT: mobile vaccination team.

sometimes intervene routinely in terms of sexual health. They informed the adolescents about the vaccination days, collected consent forms, and provided access to the infirmary when needed (quote 3).

Education assistants also sometimes helped to distribute and collect consent forms and prepared the list of adolescents to be vaccinated in addition to accompanying adolescents from the classrooms to the vaccination rooms (quote 4).

Before the vaccination days, the heads of the schools played a key role in informing and/or obtaining the approval of the school board and parents. External facilitators played a key role in coordinating stakeholders from the schools and the MVTs.

Regarding the practical organization of the vaccination days, dates were chosen in advance by agreement between the schools and the MVTs, and vaccination took place either during class hours or during lunch breaks (quote 5).

The distance between the school and the vaccination centers of the MVTs was a key factor, because travel times for the MVTs impacted the organization of the vaccination days, especially in medically underserved areas where the workload of vaccination centers is important (quote 6).

The spatial organization and available equipment for the vaccination days varied across the schools. For example, the study protocol required an available refrigerator to store vaccine doses and a water access point for hand hygiene. However, the MVTs brought vaccines in coolers, which could serve as refrigerators when needed.

### 3.3. Mechanisms of impact (acceptability and satisfaction)

#### 3.3.1. Quantitative data

Among the 1212 adolescents who completed the postvaccination questionnaire, 700 (58 %) reported that they made the decision to get vaccinated in conjunction with their parents, 290 (24 %) reported that their parents decided alone, and 211 (17 %) reported that they decided alone (11 missing data, 1 %). The adolescents' main sources of information about vaccination day(s) were their parents (562, 46 %), educational sessions at-school (463, 38 %), the school nurse (348, 29 %), teachers (327, 27 %), posters about the vaccination day (226, 19 %), and friends (167, 14 %). Before vaccine administration, most adolescents (753, 62 %) reported that they were not worried about it, although 292 (24 %) were rather worried and 163 (13 %) were very worried (4 missing data, <1 %). Among those who were worried, the main sources of concern were the fear of needles (212, 47 %) and the fear of pain (186, 41 %). At the time of the injection, 1033 (85 %) adolescents said they felt pain: 790 (65 %) reported mild, and 243 (20 %) reported intense pain. When asked how their arm felt, 352 (29 %) said it was painful, 405 (33 %) reported their arm was numb, and 456 (38 %) reported no noticeable effect. Before the injection, 179 (15 %) adolescents asked the physician or nurse questions; of these adolescents, 167 (93 %) were satisfied with the answers. With respect to overall satisfaction with the organization of the vaccination day, 1160 (96 %) adolescents were satisfied, 580 (48 %) being very satisfied, and 580 (48 %) rather satisfied.

Among the 65 professionals who completed the online questionnaire for school staff (35 teachers; others: chief education advisors, nurses and administrative staff), 51 (78 %) were satisfied with the organization of the vaccination day and 54 (83 %) reported that it had little or no impact on school life.

#### 3.3.2. Qualitative data

During the focus groups, a few members of the school staff reported that some parents were categorically opposed to vaccination for their children, and some went as far as making threats against the schools (quote 7). However, these situations were rare (quote 8).

Group effects were found to have both positive and negative
influences on the acceptability of the at-school vaccination. With respect to decision-making, some parents and/or adolescents who were convinced of the benefits of the HPV vaccination were able to help reluctant parents and/or adolescents change their mind (quote 9).

However, on the vaccination day(s), some adolescents who had just been vaccinated and those who were waiting to be vaccinated were sometimes waiting in the same room, and the former slightly discouraged the latter (quote 10).

After the HPV vaccine injection, the adolescents were provided with several documents that aimed to facilitate the completion of the HPV vaccination schedule by informing parents, family physicians and pharmacists and providing prescriptions for the second injection. However, professionals from the MVT reported that they did not use these documents in their daily practice and questioned their relevance. They stated that parents were informed because they gave consent and then got back their child's updated health records, and family physicians were informed by health records (quote 11).

## 3.4. Contextual factors (facilitators and barriers)

### 3.4.1. Quantitative data

In the activity reports, data on facilitators and barriers were available for 17/19 (89 %) schools. Among these schools, the most frequent facilitators of organizing the vaccination day(s) were the preparation by school staff of an ordered list of adolescents to be vaccinated (and its transmission to the MVT), the overall high involvement of school staff and allocated time for dedicated school staff to collect and verify parental consent forms (Fig. 2). The main barriers were the school staff's lack of time and/or the lack of human resources to organize the

vaccination day(s) (Fig. 2).

During the vaccination day(s), the most frequently reported facilitators were the availability of staff (e.g., MVTs, school nurses, and external facilitators from research teams) to complete the post-vaccination documents and call parents in case of missing health records and the high degree of involvement of the school nurse and other school staff (Fig. 2). The main barriers were missing health records, the absence of pupils at school, and the time required to complete the post-vaccination documents (Fig. 2).

### 3.4.2. Qualitative data

With regard to the organization of the vaccination days, qualitative analyses confirmed the importance of the ordered list of adolescents to be vaccinated to optimize the logistics at the schools (quote 12).

Some MVTs also prepared prescriptions for the second injection prior to the vaccination day(s), which saved time (quote 13).

Facilitators were also related to the spatial organization and available equipment in schools (quote 14) and the involvement and motivation of school staff, especially the head of the school (quote 15).

The involvement of school staff could also be hindered by several factors. For example, the limited time spent by school nurses at each school and their overwhelming number of missions without financial compensation were identified as barriers (quote 16).

Many barriers were related to parental consent forms, which were mandatory when vaccinating adolescents. The management of these forms was complicated and time-consuming for school staff because the adolescents exceeded deadlines, and several reminders had to be provided. In particular, the consent forms had to be signed by both parents, which was sometimes very difficult to achieve (e.g., in cases of deceased,

<figure><img src="image_4.png" /><figcaption>**Fig. 2.** Facilitators of and barriers to the implementation of the 'at-school vaccination' intervention based on quantitative data.</figcaption></figure>

<footnote>* Number of schools for which at least one facilitator of or barrier to the implementation of the 'at-school vaccination' intervention was reported through paper standardized activity reports among the 17/19 schools for which these reports were available.</footnote>
incarcerated, or divorced parents) (quote 17). In addition, the consent forms were provided in French only and may have been difficult for some parents to understand (quote 18).

During the vaccination day(s), attempts were made to contact parents or family physicians about missing health records, which hindered the implementation of the vaccination day (quote 19).

Finally, the COVID-19 pandemic had both positive and negative effects. On the one hand, vaccinations for COVID-19 and nasopharyngeal tests were organized in schools before the HPV vaccination day(s) and provided school staff with experience in organizing these days (quote 20). On the other hand, in the post-pandemic context, parents may have been preoccupied with other things besides HPV vaccination, and perhaps some of them refused additional vaccinations (quote 21).

## 4. Discussion

This process evaluation of an at-school HPV vaccination intervention embedded in a cRCT found that 17 % of adolescents invited returned valid consent forms to be vaccinated at school. This percentage may appear quite low compared with results achieved in countries that have long implemented routine school-based vaccination programs [17,18]. However, this percentage is underestimated, as all adolescents were invited, regardless of their HPV vaccination status, which was not known in advance. Although we could not determine the exact proportion of adolescents who had already initiated HPV vaccination, national data suggest it was approximatively 30 % among girls and 10 % among boys aged 11–14 years 2021 [32]. Moreover, this result should be interpreted considering the study context. The last national school-based vaccination campaign in France, conducted in the 1990s, has remained associated with public controversy, including among school staff [9,33]. Since then, vaccination has no longer been carried out at schools. Otherwise, the French population had also acquired an international reputation of being particularly vaccine hesitant, with 41 % having negative opinions about vaccine safety in 2016 [34].

Our results highlighted the influence of the availability and attitudes toward vaccination of various professionals on the implementation of at-school vaccination, as previously reported in the literature [19,35]. In particular, school nurses played a key role in informing adolescents before the vaccination days (together with teachers [24]), managing consent forms, and ensuring the smooth running of the vaccination day (s). However, French school nurses are not authorized to administer vaccines, so at-school vaccination requires the participation of an external health professional as MVT. This organizational model has the advantage of relying on teams experienced in such activities; however, it also introduces additional complexity due to the need for coordination between schools and MVTs. Before 2023, only physicians were authorized to prescribe and administer vaccines in France. Since then, nurses and community pharmacists have been allowed to both prescribe and administer vaccines to targeted individuals aged 11 and older (although in practice, school nurses still do not) [36]. This change may help increase human resources for MVTs and facilitate at-school vaccination.

Our results also highlighted the key role of parents as a source of information for adolescents and in decision-making regarding HPV vaccination, as already shown [19,20,35]. As we previously reported [24], the 'education and motivation' intervention preceding 'at-school vaccination' in our study failed to reach parents through webconferences. International studies have identified other promising strategies, and their feasibility could be assessed in France: e.g., providing information about HPV vaccination the school year before vaccination, using decision-aid tools to promote shared adolescent-parent decision-making, calling parents who did not return consent forms using motivational interviewing techniques [37–40]. Particular attention should be paid to provide tools tailored to parents' needs and that are not overly complex, especially for non-French-speaking parents [41]. These strategies may also improve the return of consent forms, which was challenging, as observed in other countries [15,19,35,37]. One particular challenge was

obtaining valid consent signed by both parents. Indeed, according to French law, the free, informed, and clearly expressed consent of both parents (i.e., an opt-in approach) is required to vaccinate a minor. While shifting from an opt-in to an opt-out approach could positively impact HPV VC [15], such an approach is not legally permitted in France. Processes to obtain parental consent may benefit from using simplified and shortened consent forms, reminder systems, and integrating new technologies [15,42].

Another challenge in our study was ensuring that adolescents brought their health records on vaccination day(s). Unlike in some other countries [35], there is no nationwide vaccination registry to verify adolescents' vaccination status in France. One way to address this issue could be to check health records in advance. Adolescents' fear of needles and pain may also negatively impact the overall flow of the vaccination day(s) [19]. The use of decision-aid tools [43] or more specific interventions (e.g., the Comfort Ask Relax Distract vaccine delivery framework) [44] may help reduce adolescents' fear. Finally, we found that placing adolescents who had just been vaccinated in the same room as those waiting to be vaccinated could have negative consequences. Organizing the rooms according to a linear pathway could improve both the efficiency of vaccination-day processes and the vaccination experience for adolescents [37], although this may be challenging to implement in some schools.

On the basis of these findings, we formulated recommendations for the implementation of HPV vaccination campaigns at schools (Fig. 3). This may be particularly helpful as the French government decided to generalize at-school HPV vaccination among 7th-grade pupils since autumn 2023 [45], partly based on preliminary conclusive results of our study and previous regional experiments [46]. This gender-neutral strategy can effectively promote equity in HPV vaccination [47] and reduce territorial disparities resulting from inequalities in healthcare access [23]. In a next step of our study, we plan to assess its cost-effectiveness [22]. Beyond the potential improvements discussed above, other strategies could further enhance the efficiency of at-school vaccination, although they would require changes in the legislative framework and strong support from policymakers. For example, the Ministry of Education could authorize school nurses to vaccinate pupils and ensure that schools have adequate staff resources. The parental consent procedure could also be simplified by requiring the signature of only one parent. Finally, some studies suggested that initiating HPV vaccination at a younger age (9–10) might increase coverage, although the supporting evidence is limited [48].

This study has several strengths. First, the process evaluation used a mixed methods design, and was conducted according to the recommendations of the MRC for process evaluation of complex interventions [26]. Second, it was embedded in a large national pragmatic trial in which the intervention was implemented under conditions similar to routine practice. However, we must also acknowledge several limitations. First, to ensure the feasibility of the trial, we limited it to municipalities with only one middle school and thus excluded all large French municipalities and larger schools [49]. Generalization of the present results to the largest French middle schools or urban environments should be performed with caution. Second, one-third schools dropped out before implementing the intervention and not all adolescents were invited to be vaccinated at school. However, analyses accounting for the dose of intervention allowed us to take this into account when estimating the effectiveness of the intervention [24]. Third, we did not collect data from parents and adolescents who did not agree to receive vaccination at school. It would have been interesting to explore their perspectives and the underlying reasons for their refusal. Fourth, some focus groups included only a small number of participants. Nevertheless, collective interviews can still yield valuable insights when participants are highly engaged with the topic [30]. Participants in the focus groups might have had more polarized attitudes toward the intervention than non-participants, such as those who participated in the online survey, for which we could not estimate the response rate.
<figure><img src="image_5.png" /><figcaption>**Fig. 3.** Key recommendations for implementing HPV vaccination at-school on the basis of the results of the process evaluation within the PrevHPV trial. HPV: human papillomavirus; MVT: mobile vaccination team.</figcaption></figure>

## 5. Conclusions

This process evaluation of the ‘at-school vaccination’ component of the PrevHPV intervention, which was effective in increasing HPV VC, provided a detailed description of how vaccination days were prepared and implemented in schools and showed high acceptability among adolescents and school staff. The results led to the formulation of recommendations for the implementation of HPV vaccination campaigns at school, which may be particularly helpful as part of the school HPV vaccination campaigns that have been generalized in France and may be applicable in other countries.

## Authors’ contribution

A.B., S.B., A-S.L-D-B., A.G., S.B., A-G-B., B.G., M.M., J.E.M. and N.T. conceptualized and designed the study. A.B., S.B., M.B. and A.G. performed the data collection. A.B. and S.C. performed the quantitative data analyses. A.B., S.C., E.F. and S.B. performed the qualitative data analysis. A.B. and S.C. wrote the original draft, and B.L. and N.T. performed the review and editing. All the authors have read and approved the final manuscript.

## CRediT authorship contribution statement

**Aurélie Bocquier:** Writing – review & editing, Writing – original draft, Supervision, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Simon Cadoret:**

Writing – review & editing, Writing – original draft, Formal analysis. **Estelle Fall:** Writing – review & editing, Supervision, Methodology, Formal analysis. **Stéphanie Bonnay:** Writing – review & editing, Project administration, Investigation, Formal analysis, Data curation, Conceptualization. **Anne-Sophie LeDuc-Banaszuk:** Writing – review & editing, Supervision, Funding acquisition, Conceptualization. **Marion Branchereau:** Writing – review & editing, Investigation. **Aurélie Gauchet:** Writing – review & editing, Methodology, Investigation, Funding acquisition, Conceptualization. **Sébastien Bruel:** Writing – review & editing, Funding acquisition, Conceptualization. **Amandine Gagneux-Brunon:** Writing – review & editing, Funding acquisition, Conceptualization. **Bruno Giraudeau:** Writing – review & editing, Funding acquisition, Conceptualization. **Morgane Michel:** Writing – review & editing, Funding acquisition, Conceptualization. **Judith E. Mueller:** Writing – review & editing, Funding acquisition, Conceptualization. **Benjamin Lefèvre:** Writing – review & editing, Supervision. **Nathalie Thilly:** Writing – review & editing, Supervision, Project administration, Methodology, Funding acquisition, Conceptualization.

## Funding

The study was conducted with the support of IReSP and financial support from ITMO Cancer AVIESAN (Alliance Nationale pour les Sciences de la Vie et de la Santé/National Alliance for Life Sciences & Health) within the framework of the Cancer Plan.
Declaration of competing interest

The authors declare the following financial interests/personal re-
lationships which may be considered as potential competing interests:
The PrevHPV Study Group reports financial support was provided by
ITMO Cancer AVIESAN. Gagneux-Brunon reports a relationship with
MSD, Moderna, and Pfizer that includes: speaking and lecture fees and
travel reimbursement. Gauchet reports a relationship with MSD, Mod-
erna, and Pfizer that includes: speaking and lecture fees and travel
reimbursement. If there are other authors, they declare that they have no
known competing financial interests or personal relationships that could
have appeared to influence the work reported in this paper.

Acknowledgments

The PrevHPV study group includes the authors of the present
manuscript and the following. For Team 1: Maïa SIMON; for Team 2:
Marie ECOLLAN, Serge GILBERG, Josselin LE BEL, Henri PARTOUCHE,
Juliette PINOT, Louise ROSSIGNOL, Arthur TRON, Dragos-Paul HAGIU;
for Team 3: Catherine JUNEAU, Julien AILLOUD; for Team 5: Florian
JEAN LEBOEUF, Géraldine JAMBON, Elisabeth BOTELHO-NEVERS,
Emilie DARLINGTON, Mabrouk NEKAA; for Team 6: Karine CHEV-
REUL; for Team 7: Jocelyn RAUDE, Jonathan SICSIC, Anne-Sophie
BARRET, Sandra CHYDERIOTIS, Damien OUDIN-DOGLIONI, Josée
DUSSAULT; Clémence CASTAGNET (Inserm/PRC) and Mélanie
SIMONY (IReSP).

The authors would like to thank the representatives of the following
institutions who participated in the steering committee of the research
program: Inserm, IReSP, ITMO Cancer AVIESAN, ITMO Public Health
AVIESAN, INCa (the French National Cancer Institute), the French
Public Health Agency (Santé publique France), the Ministry of Health,
the Ministry of National Education, especially Dr. Brigitte MOLTRECHT
from the Direction générale de l'enseignement scolaire, and the Ile-de-
France Regional Health Agency.

The authors also want to thank all of the professionals who partici-
pated in the working groups and all individuals who agreed to partici-
pate in the diagnostic and/or co-construction phase of the PrevHPV
program.

Finally, the authors thank the heads of the 91 middle schools who agreed to participate in the PrevHPV study; their staff members; the pupils and parents who participated in the study; and the staff of the vaccination centers involved in the vaccination of adolescents at school.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.
org/10.1016/j.vaccine.2025.128122.

Data availability

Data will be made available on request.

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