A scoping review of randomised controlled trials of vaccines that recruited care home residents: lessons for future trials

Introduction: Older care home (CH) residents are particularly vulnerable to infections and often experience adverse outcomes. Despite this group being frequently prioritised for vaccinations, trials of vaccines rarely recruit CH residents. Given that the social and biological characteristics of CH residents may influence vaccine effectiveness, it is crucial to test vaccines in this population. 
Methods: The Widening Access to Trials in Care Homes project was established to develop best practice guidance on designing and conducting vaccine trials in the CH population. As part of this project, a scoping review following Joanna Briggs Institute methodology was conducted to identify vaccine trials involving CH residents. Search conducted in EMBASE, MEDLINE, PsycINFO, CINAHL and Cochrane Library, from 1990 to 2025. 
Results: presented as descriptive summaries. Results We retrieved 701 articles and included 20 studies. A total of 7479 participants from 238 CHs were recruited to influenza or pneumococcal vaccine trials. The weighted mean age was 82.3 years. Screen failure averaged 70% (eight studies), primarily due to declining participation (46%) and not meeting eligibility criteria (27%). Dropout averaged 8% (11 studies), with death (21%) being the most common reason. Identified barriers include eligibility criteria and recruitment, consent and assent issues, ethical and regulatory, CH-related factors and study time frame and logistical factors. Facilitators include recruitment and data collection methods, consent and assent factors and collaboration with CHs. 
Conclusion: Our review is the first to synthesise both quantitative and qualitative evidence on recruiting CH residents into vaccine trials and to provide suggestions for future trial design in this population.