Page 54 - Preventing pertussis in early infancy - Visser

Chapter 4
Quantitative study parents
behaviour. Intention in turn is determined by the attitude towards the behaviour (e.g. how does a person feel about accepting a vaccination), the perceived social norm towards the behaviour (e.g. how does a person think important others feel about accepting a vaccination), and the control people perceive to have over the behaviour (e.g. does a person think he is able to get vaccinated and does he think he is the one who has the autonomy to decide). In addition to the psychosocial determinants of the RAA, our qualitative study showed the importance of anticipated negative affect (e.g. does a person foresee any negative feelings as a result of the acceptance or non-acceptance of the vaccination?) and decisional uncertainty (e.g. does a person find it easy to decide whether to accept a vaccination or not?). We therefore added these psychosocial determinants to the potential determinants of intention in the theoretical framework for this study. Furthermore, various factors came forward from both the previous study and literature that seemed to influence parental attitude. In the RAA these factors are called attitudinal beliefs and we added them to the theoretical framework as potential determinants of attitude. Figure 1 shows the final theoretical framework on which the questionnaire was based.
Variables
The primary outcome measure in the questionnaire was the parental intention to accept a pertussis vaccination if offered in the context of a cocooning strategy (Figure 1). Furthermore, we measured both personal and psychosocial determinants that potentially influence the parental intention to accept vaccination as well as potential determinants of attitude. Figure 1 shows an overview of the measures within psychosocial determinants of intention and the determinants of attitude. Personal determinants of intention included personal data (age, gender, education, income, etc.), vaccination data (own vaccination status within the National Immunisation Programme (NIP), etc.), and pertussis experience (experience with adults with pertussis, etc.). They were measured using 16 multiple-choice items, adapted to the Netherlands serosurveillance project PIENTER 2 (National institute for Public Health and the Environment, RIVM website accessed September 2012).
The primary outcome measure (intention), the psychosocial determinants of intention, and the determinants of attitude were measured with 7-point Likert scales. Items were combined based on content and when internal consistency proved sufficient (Cronbach’s Alpha α > 0.70 or Pearson correlation r > 0.60). For each participant these items were then merged into one single measure by calculating the average score, but only if the participant answered at least 60% of the items within the measure.
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