SOW conceived the study. SOW and JB designed the study. SOW and LL collected the data.

Objective: To administer the Parent Attitudes Childhood Vaccines (PACV) questionnaire to assess vaccine hesitancy and its relationship with non-vaccination. Design: A cross-sectional study using the 15-item PACV questionnaire, with sociodemographic questions. Setting: Outpatient department in a tertiary paediatric hospital, Dublin, Ireland. Participants: Parents/caregivers of children attending general paediatric clinics. Main outcome measures: PACV score and reported non-vaccination. We assessed sociodemographic factors associated with PACV score and accuracy of the PACV in predicting non-vaccination. Results: In total, 436 participants completed the questionnaire. 5.5% of our population reported non-vaccination. HPV and MMR vaccines were the most commonly cited vaccines of concern (11.5% and 6.7% respectively) and autism spectrum disorder was the most commonly side effect of concern (4.3%). Mean PACV score was 26.9 (SD 19.1), with a significant difference between non-vaccinators and vaccinators (53.2 vs 25.3, p<0.001). Safety and efficacy concerns were the major contributor to non-vaccination. 14.4% of our population were vaccine-hesitant using the conventional cut-off score, which increased to 22% when using an optimal cut-off which maximised sensitivity and specificity. The accuracy of the PACV score to identify non-vaccination was good (area under the ROC curve = 0.827) and the optimal cut-off had a high negative predictive value (98.5%). Conclusions: PACV identified non-vaccination with high accuracy in our population. It may be useful to screen vaccine hesitant parents who could benefit from interventions to improve uptake.