<p>Children with inflammatory bowel disease are at increased risk of infectious diseases, including vaccine-preventable infections, due to immune dysregulation and immunosuppressive therapy. Data on the persistence of protective antibodies against measles and rubella in this population remain limited. To evaluate the seroprotective levels of IgG antibodies to measles and rubella in children with IBD and identify factors associated with antibody loss. A prospective observational study included 93 pediatric patients with IBD. IgG antibodies against measles and rubella were measured using ELISA. Vaccination status, clinical activity indices (PUCAI, PCDAI), and immunosuppressive therapies were documented. Survival analysis using Cox regression assessed factors influencing antibody persistence. Seroprotection rates were 65.5% for measles and 76% for rubella. Complete vaccination was achieved by 68.2% and 72% of patients for measles and rubella, respectively. Patients with full vaccination had significantly higher antibody levels. Younger age (&lt;6 years) was associated with an increased risk of antibody loss: for measles, HR 21.58 (95% CI 4.46 – 104.40, p &lt; 0.001), and for rubella in univariate analysis, HR 6.44 (95% CI 1.47–28.19, p=0.013). Incomplete vaccination increased the risk of antibody loss for measles (HR 2.76; 95% CI 1.31 – 5.79; p=0.007) and rubella (HR 2.53; 95% CI 1.06 – 6.01; p=0.036) in univariate analyses, but lost significance after adjustment in multivariate models. Immunosuppressive therapy did not significantly affect antibody levels. The highest risk groups for antibody loss were identified as High risk for measles (70% loss) and Intermediate-High risk for rubella (50% loss). In children with IBD, completed vaccination does not always guarantee protective antibody levels. Younger age and incomplete vaccination are key predictors of antibody loss. These findings highlight the need for personalized vaccination strategies and regular serological monitoring in this vulnerable population.</p>