'Why did nobody ask us?': A mixed-methods co-produced study in the United Kingdom exploring why some children are unvaccinated or vaccinated late

Objective: Childhood vaccine uptake in the United Kingdom (UK) is sub-optimal leading to outbreaks of preventable diseases. We aimed to explore UK parents' perspectives on why some children are unvaccinated or vaccinated late. Methods: We undertook a mixed-methods, co-production study involving a survey using a questionnaire followed by focus groups. We partnered with The Mosaic Community Trust (Mosaic) who are based in a more deprived, ethnically diverse, low vaccine uptake area of London. Targeted recruitment to complete the questionnaire (either on paper or online) was done through Mosaic, community networks and social media promotion. We collected demographic data alongside parents' views on routine childhood vaccination, their vaccine decisions, and experiences of accessing childhood vaccine appointments We report descriptive findings from the questionnaire and thematic analysis of free-text questionnaire answers and focus groups guided by the COM-B model of Capability, Opportunity, and Motivation. Results: Between June-October 2022, 518 parents were surveyed of whom 25% (n = 130), were from ethnic minorities (13%, n = 68-unknown ethnicity). In 2023 we held four focus groups with 22 parents (10 from ethnic minorities). Only 15% (n = 78) parents had delayed or refused a vaccine for their child. A quarter of parents felt they had not been given enough information nor an opportunity to ask questions before their children's vaccinations. Inconsistent reminders and difficulties booking or attending appointments impacted vaccine uptake with negative experiences influencing future vaccine decisions. Parents had mixed views on vaccinations being given in different locations and wanted trusted health professionals to vaccinate their children. Conclusion: To reverse declining vaccine uptake and prevent future outbreaks it needs to be easier for UK parents to speak to health professionals to answer their childhood vaccine questions, alongside simplified booking systems and easier access to routine childhood vaccine appointments.