We conducted a longitudinal study of influences on pH1N1 vaccination behaviour in Hong Kong to test this model ( Figure 3) , and subsequently followed up participants to record their selfreported receipt of pH1N1 vaccine. In this study, we aimed to answer the following research questions: How well does intention predict future uptake of pH1N1 vaccine? Does vaccination planning mediate the relation between intention and future vaccination uptake? And do the original TPB components and the additional components (extended social norms, anticipated regret and seasonal influenza vaccination history) contribute to peoples' decisions on vaccination uptake? 