Men who have sex with men (MSM) are more vulnerable to human papillomavirus (HPV) infection than the general population, and have an increased risk of associated illnesses, including genital warts and oropharyngeal, anal, and penile cancer. HPV vaccination is highly effective at reducing new HPV infection and reducing persistent infection in MSM , which has led some countries to develop targeted vaccination programmes offering free HPV vaccination to MSM. However, uptake for these programmes internationally remains low. One potential route to ameliorating this low uptake is a burgeoning area of research within social norms: the dynamic framing of counter-normative messages, where target behaviours are framed as becoming increasingly common. While the use of social norms in health promotion relies on many people already performing the desired behaviour, dynamic norms may be effective at impacting on less popular behaviours. Additionally, research suggests connectedness to the LGBT+ community may be an important factor when considering norm-related behaviour in LGBT+ individuals. Research on vaccination behaviours in LGBT+ population suggests the influence of common reference groups (family, friends, and community) for other populations may not be as influential in those in the LGBT+ community. This project aims to explore HPV vaccination in MSM in Ireland. The online Qualtrics study consists of a between-subjects experiment embedded in a cross-sectional survey. The experiment will test the effect of dynamically framed norm messaging on HPV vaccine intention. Participants will be randomised to one of three conditions (control/no norms, static norms, dynamic norms). The survey also investigates the social cognitive predictors (Health Belief Model (HBM) and Theory of Planned Behaviour (TPB)) of HPV vaccination in MSM, and the moderating effect of connectedness to the LGBT+ community.