Background: Patients with inflammatory bowel disease (IBD) have a higher risk of infection and are frequently not up to date with their immunizations.

Objectives: This study aims to review vaccination status and evaluate whether age, disease type, or treatment regimen could predict the absence of seroprotection against selected vaccine-preventable infection in adults with IBD.

Methods: Cross-sectional study using questionnaire, immunization records review, and assessment of tetanus-specific, varicella-specific, and measles-specific immunoglobulin G concentrations. ClinicalTrials.gov: NCT01908283.

Results: Among the 306 adults assessed (median age 42.7 years old, 70% with Crohn's disease, 78% receiving immunosuppressive treatment), only 33% had an immunization record available. Absence of seroprotection against tetanus (6%) was associated with increasing age and absence of booster dose; absence of seroprotection against varicella (1%) or measles (3%) was exclusively observed in younger patients with Crohn's disease. There was no statistically significant difference in immunoglobulin concentrations among treatment groups. Although vaccinations are strongly recommended in IBD patients, the frequencies of participants with at least 1 dose of vaccine recorded were low for nearly all antigens: tetanus 94%, diphtheria 87%, pertussis 54%, poliovirus 22%, measles-mumps-rubella 47%, varicella-zoster 0%, Streptococcus pneumoniae 5%, Neisseria meningitidis 12%, hepatitis A 41%, hepatitis B 48%, human papillomavirus 5%, and tick-borne encephalitis 6%.

Conclusions: Although many guidelines recommend the vaccination of IBD patients, disease prevention through immunization is still often overlooked, including in Switzerland, increasing their risk of vaccine-preventable diseases. Serological testing should be standardized to monitor patients' protection during follow-up as immunity may wane faster in this population.