Statistical analysis was performed using SPSS version 15.0 (SPSS Inc., USA). The x 2 test or Fisher's exact test was used to explore the statistical differences between categorical variables. The independentsamples t test was used to compare statistical difference between continuous variables in two groups. The one-way between-groups analysis of variance (ANOVA) was used to explore the differences between more than two groups. Logistic regression was performed to explore the impact of the variables on vaccination status. The two-step cluster analysis procedure was performed to explore the natural groupings (i.e. clusters) within the respondents. The clustering criterion was that the solution had smaller values of Schwarz's Bayesian Information Criterion (BIC), a reasonably large ratio of BIC changes and a large ratio of distance measures. A P value <0 . 05 was considered to denote statistical significance.