Perceived self-efficacy. One item was used to measure selfefficacy, asking about respondents' agreement on a 5-point scale with the statement ''I am confident that I can go independently to get human swine flu vaccination''. A standard scale of self-efficacy was not adopted to minimize assessment load. However, a single item for self-efficacy has been shown elsewhere to have validity in predicting behavioural change [59, 60] .