Effect of choice of measles-mumps-rubella vaccine on immediate vaccination pain in infants.

OBJECTIVE To compare acute pain response to 2 measles-mumps-rubella vaccines. DESIGN Double-blind clinical trial. SETTING Hospital for Sick Children, Toronto, Ontario. Patients Forty-nine infants 12 months of age receiving their first measles-mumps-rubella vaccination. INTERVENTIONS Random allocation to receive Priorix or M-M-R II. MAIN OUTCOME MEASURES Pain responses before (baseline) and after (within 15 seconds) vaccination were quantified by visual analog scale (VAS; range, 0-100), completed by the parent and independently by the pediatrician, and the Modified Behavioral Pain Scale (range, 0-10), scored by a coder blinded to the vaccine allocation. Crying (yes or no) and latency to the first cry after injection were also measured. RESULTS Twenty-six infants received Priorix and 23 received M-M-R II. There were no differences between the 2 groups in baseline characteristics or prevaccination baseline pain scores. Median pain scores after vaccination (Priorix vs M-M-R II) were as follows: pediatrician VAS, 15 vs 58 (P =.001); parent VAS, 22 vs 53 (P =.007); and Modified Behavioral Pain Scale, 6 vs 8 (P =.02). Median difference in pain scores (after minus before) for Priorix vs M-M-R II were as follows: pediatrician VAS, 15 vs 53 (P =.003); parent VAS, 22 vs 47 (P =.008); and Modified Behavioral Pain Scale, 3 vs 5 (P =.03). The median latency to first cry was 1.5 seconds in the Priorix group compared with 1 second in the M-M-R II group (P =.26). CONCLUSIONS Priorix vaccine causes significantly less pain than M-M-R II at the time of injection for 12-month-old infants receiving their first measles-mumps-rubella vaccination.