Patients with inflammatory bowel disease (IBD) are often on immunosuppressive therapies which may reduce the immunologic response to the SARS-CoV-2 vaccine. At this time, there is limited data on vaccine response in patients on different therapies. Furthermore, the CDC does not recommend antibody testing to confirm immunity, and revaccination is not recommended.
Our study evaluated antibody response measured by a quantitative IgG antibody to the spike antigen of SARS-CoV-2 via ELISA in a group of 73 vaccinated IBD patients who have undergone or are receiving infusions of vedolizumab, infliximab, and ustekinumab, or a combination of multiple biologics. All patients have received the 2-dose vaccination and must have completed them for minimum 2 weeks or longer before testing. Statistical analysis was performed by segmenting the patient population into two subgroups of normal ( >20 U/mL) and abnormal (< 20 U/mL) titer levels. Independent T-tests were then performed on specific patient characteristics, inflammatory markers, and medications to determine statistical significance.
Responses greater than 20 IU/mL were considered normal responses. Patients older than age 50 were more likely to have abnormal antibody titers after vaccination. There were no differences in antibody response when comparing patients on different biologics including those that were on more frequent dosing (q4 week injections/ infusions vs q8 weeks, or between ulcerative colitis (UC) vs. Crohn’s disease (CD), or in those with biomarker evidence of active disease based on erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) (See Table 1). None of these patients, including those with abnormal titer levels developed COVID infection after vaccination.
In our study, it was found that only age was a statistically significant predictor among our immunosuppressed IBD patients for antibody response levels. Importantly, even more aggressive combination biological therapies did not appear to affect antibody response in our patient population. Lastly, inflammatory markers and presumably disease activity, did not appear to have a statistically significant impact on antibody response. More studies will be needed to further assess if there is clinical utility in evaluating for vaccine antibody titers in our IBD patients.