<p>PLOS ONE inclusivity questionnaire.</p>

The introduction of the human papillomavirus (HPV) vaccine in Nigeria in October 2023 aimed to vaccinate over 16 million adolescent girls through mass vaccination campaigns in schools, communities, and public places. Despite this initiative, many girls remain unvaccinated, particularly in some of the states included in the first phase of the rollout. Little is known about the perspectives of parents and caregivers who consent on behalf of their daughters regarding the HPV vaccine. This paper presents a qualitative study protocol and research design to explore what informed parents and caregivers’ acceptance or refusal of the HPV vaccine for their adolescent daughters during the campaign. Semi-structured in-depth interviews will be conducted with parents and caregivers of girls aged 9–14 years, attending both private and government primary and secondary schools in Ilishan, Ogun State, Nigeria. Participants will be purposively recruited from schools where the mass HPV vaccination campaign was implemented, with a focus on parents and caregivers who provide consent to take part in the study, regardless of whether they accepted or refused the HPV vaccination for their daughters when it was offered. Approximately 30 parents and caregivers will be interviewed until data saturation is reached and no new themes emerge from the data. Interviews will be transcribed verbatim and, where necessary, translated. Data will be coded and analysed thematically in an iterative process, allowing for the identification of key themes and patterns. This study aims to provide valuable insights into how parents perceive the HPV vaccine and the factors that informed their vaccination decisions. Findings will contribute to the development of context- and culturally-sensitive vaccination strategies, enhancing the success of HPV vaccination campaigns and supporting the global effort to eliminate cervical cancer.