This study is a 2-arm, parallel, randomised controlled feasibility trial of a brief video intervention designed to induce positive affect (mood) in older adults in primary care settings prior to the receipt of influenza vaccination. Participants will be randomised into two conditions: experimental and active control. In the experimental condition, participants will view the approximately 15 minute long intervention video immediately prior to vaccination. In the active control condition, participants will view a matched video that is designed to be mood neutral. Pre-and-post positive affect levels will be assessed by self-report questionnaires. Immune response to the intervention and vaccination responses will be assessed in saliva and serum samples respectively.