Purpose of the Review <p>This review explores the current evidence of (1) the association between sleep, insomnia, and immune functions, (2) sleep and insomnia as modulators of influenza vaccine responses, (3) the potential implications for health psychology interventions.</p> Recent Findings <p>Sleep promotes innate and adaptive immune processes which are crucial to build an efficient response to vaccination, while insomnia is associated with increased inflammation and lower antibody production following vaccine injection. Psychological interventions such as cognitive behavioural therapy and mindfulness have remarkable effects in improving sleep quality and reducing insomnia and may potentially restore immune functioning. Whether sleep interventions may boost immune responses to influenza vaccine remains to be explored.</p> Summary <p>Seasonal influenza remains a significant public health challenge worldwide, with millions of symptomatic cases and hundreds of thousands of deaths annually. Vaccines show only moderate efficacy due to the highly rapid viral evolution. In this context, sleep medicine may offer a paradigm shift in influenza prevention by focusing on individual (host) characteristics to potentiate immune response to vaccine.</p>