LAUSR

BACKGROUND Infection is believed to be a potential trigger for inflammatory bowel disease (IBD). Whether vaccination against childhood infections including measles, mumps, and rubella may reduce risk of IBD is uncertain. METHODS We conducted a retrospective cohort study using de-identified claims data from a national private payer (Optum Clinformatics Data Mart). Eligible infants were born between 2001 and 2018 and were continuously enrolled with medical and pharmacy coverage from birth for at least 2 years (n = 1 365 447). Measles, mumps, and rubella vaccination or MMR is administered beginning at 12 months of age. Cox proportional hazard regression models were used to compare time with incident disease in children by category of vaccination, after adjustment for sex, birth year, region of country, history of allergy to vaccines, and seizure history. RESULTS The incidence of early pediatric IBD increased between 2001 and 2018. Ten percent (n = 141 230) of infants did not receive MMR, and 90% (n = 1 224 125) received at least 1 dose of MMR. There were 334 cases of IBD, 219 cases of Crohn's disease, and 164 cases of ulcerative colitis. Children who had received at least 1 dose of MMR had lower risk for IBD than children who did not (hazard ratio, 0.71; 95% confidence interval, 0.59-0.85). These associations did not change after further adjustment for childhood comorbid conditions, preterm birth, or older siblings affected with IBD. Similar associations were observed for MMR with Crohn's disease and ulcerative colitis, although these did not reach statistical significance. CONCLUSION MMR is associated with decreased risk for childhood IBD.