Hong Kong has 99% landline telephone penetration, local calls are free and telephone interviews are common and representative methods of survey data collection [53] . We conducted 13 main cross-sectional telephone surveys of psychological and behavioural responses to the first wave of the 2009 influenza A/H1N1 pandemic in Hong Kong from April through November 2009 (the parent study) [53] in order to monitor these variables. As an extension, the present study re-contacted subjects from some of these surveys and sought to understand public decision-making regarding pH1N1 vaccine uptake for mitigating the potential second wave of the pandemic. Between 12-25 January, 2010 a baseline assessment for the present study was performed, immediately prior the local pH1N1 vaccination campaign extending to the general community (vaccination for high risk groups started from December 21, 2009), and we again contacted participants for follow-up two months later, between 15-30 March 2010.