Unravelling the social–brain–immune link: Social engagement, reward pathways, and health from big data to intervention

Renewed awareness of the fundamental importance of social connection has emerged in the post-pandemic era, with supportive relationships recognised as vital to health and survival as food or water. Decades of research show isolation and loneliness increase inflammation and impair antiviral defence. The critical next step is to determine whether and how actively increasing social engagement can causally strengthen immune defences. Addressing this gap will clarify mechanisms, identify those most at risk, raise clinical awareness, and guide interventions.SocialImmunity introduces an innovative framework integrating population-scale modelling with mechanistic experimentation to investigate how social engagement improves antiviral immune responses. The central hypothesis is that reward-related brain circuits mediate immune benefits of positive social interactions. Evidence from animal studies suggests dopaminergic activation, triggered by rewarding social experiences, enhances innate and adaptive immunity, yet this pathway remains untested in humans.The project pursues three objectives: (1) examine whether social engagement is associated with antiviral immune markers at the population level, and test mediation by reward-related brain connectivity using advanced modelling; (2) develop and pilot a social engagement intervention to assess feasibility and its effect on reward motivation; and (3) test causality by conducting a randomised controlled trial to determine whether increasing social engagement enhances vaccine-induced antibody response, and whether this effect is mediated by reward-related mechanisms.By integrating epidemiological evidence with mechanistic experimentation, SocialImmunity will advance understanding of how social engagement contributes to immune resilience and reward-related neural pathways. SocialImmunity can inform low-cost strategies to improve health, reduce vulnerability to infection, and combat loneliness through scalable interventions.