Study limitations include baseline attitudes/beliefs, vaccination intention and planning being measured at the same time point, prohibiting exploration of causality in observed associations. Some study measures were constrained due to length of telephone interviewing, and while sub-optimal were necessary methodological compromises. Although most researchers recommended Cronbach's a of 0.7 as the minimal acceptable for internal consistency of multi-item scales, others accept 0.6 or 0.5-0.6 for preliminary research as the cut-off point [56] . Other than dimensionality concerns, lower a can reflect too few items comprising the putative scale [73] . This is more likely for complex variables, such as social norms which have a broad spectrum of elements. Though less than perfect, measurement errors can be reduced by incorporating the items as a latent variable in SEM [55] , an approach we adopted. Additionally, collinearity between exogenous indicators, such as social norms and perceived benefit can be potentially problematic, perhaps lowering the accuracy of SEM estimation. However, since high associations between measures of the constructs were not observed (Table 3) then collinearity-related error is probably small [74] . Despite being randomly selected for the parent study, subjects of this study were not randomly selected from the general population, although demographics suggest the current sample is comparable to the Hong Kong general population [61] (Table 2 ). Moreover, subject recruitment was based on voluntariness and all data were selfreported. All could cause social desirability and selection bias, so caution is needed before extrapolation to the general population. Also refusal at follow-up could have influenced patterns of responses. Our study examined public decision-making regarding a novel influenza pandemic vaccine. Our findings may not apply to vaccination against seasonal influenza due to numerous differences in beliefs towards the vaccination. For example, although perceived low risk remains the major reasons for refusing vaccination against seasonal influenza as in our study, vaccine safety is seldom cited as a barrier [28, 29] whereas we found that about one third of respondents had vaccine safety concerns. Cultural differences in influenza and vaccination-related beliefs are possible [75] , but these differences may gradually diminish with the increasing identical news information available through the three dominant news agencies and common public health strategies being increasingly universal. Related stories, such as use of preservatives and adjuvants in vaccine manufacture may enhance knowledge and reduce trust in product safety [76] . The role of media remains much under-researched in this regard. Finally, data was insufficient to reliably report the reasons for pH1N1 vaccination uptake among the population.