However, this does not explain why family size was not related to MMR: there was a wider range of family sizes in the MMR group (parents with a maximum of six children in the family) than in the dTaP/IPV group (with a maximum of only

four children in the family). For MMR, it is possible that apprehensive parents may want to make separate decisions for each child based on information available check details at the time; as found in some of the interviews with parents of preschool children [4]. Alternatively, there may be a critical number of children beyond which any additional children make no difference so that the different family sizes in the two groups gave an artificial result. Clearly, however, a larger study would be needed to investigate these assumptions further. Although subjective norm was found to correlate with intention, it was interesting that this did not predict parents’ intentions to immunise with either MMR or dTaP/IPV. This suggests that friends, family and healthcare professionals did not directly influence parents’ immunisation intentions, even drug discovery though in the interviews most parents said that they would attend for immunisation

because it was ‘the norm’ [3] and [4]. Thus, although parents may discuss their vaccine decisions with these ‘significant others’, these discussions may not directly influence their child’s immunisation status. Indeed, Bennett and Smith [9] found that there was no difference in the families’ or friends’ perceptions of the value of immunisation between those caregivers who had fully vaccinated a child against

pertussis, partially completed the course or refused pertussis vaccination. This finding is also supported by earlier TPB-based research which found that subjective norms were unrelated to immunisation status [13] and [14]. Moreover, across studies and across a range of health behaviours, attitude and perceived control generally emerge as stronger predictors of intention Linifanib (ABT-869) [19]. Hence, the findings of the present study suggest that, when it comes to preschool immunisation, other factors are more salient than the views of ‘significant others’. Overall, the predictors identified in the regression analyses accounted for 48.0–64.4% of the variance in parents’ intentions to immunise with a second MMR and 52.1–69.5% of the variance in parents’ intentions to immunise with dTaP/IPV. This is consistent with the finding that attitude, subjective norm and perceived control generally account for 40–50% of the variance across studies and health behaviours [19]. Prediction rates were impressive, with 84.0% and 83.7% of parents correctly classified for MMR and dTaP/IPV, respectively. Therefore, by including attitudes and beliefs identified in interviews with parents, the IBIM generated highly predictive models of uptake.