Neutralizing Antibody Response to SARS-CoV-2 Variants After Two mRNA COVID-19 Vaccine Doses in a Cohort of Patients with Inflammatory Bowel Disease from a Southern Italy Tertiary Hospital

<b>Introduction:</b> Inflammatory bowel diseases (IBDs) require immunosuppressive drugs like biologics. All IBD patients, including those on biological therapy, should be vaccinated against COVID-19, according to the ECCO recommendations. IBD patients on anti-TNF treatment exhibited lower COVID-19 vaccine responses; however, SARS-CoV-2 variant neutralizing antibody titers have been seldom studied. <b>Methods:</b> IBD patients and healthcare professionals (control group) were tested for COVID-19 vaccine immunogenicity by neutralizing antibody titers against Wild-Type SARS-CoV-2 and its variants. IBD patients were assigned to no treatment/mesalamine, anti-TNF biologic therapy, or non-anti-TNF biologic therapy. The study was performed in a tertiary hospital in Palermo, Sicily, from May to July 2021. <b>Results:</b> In total, 107 IBD patients and 41 healthcare workers were enrolled. A total of 46 patients received mesalamine or no medication, 28 received anti-TNF biologics, and 33 received non-anti-TNF biologics. No significant differences were found in age, gender, or timing of blood sampling post vaccination. Omicron neutralizing activity was markedly reduced in all groups (<i>p</i> < 0.001). The group of patients on anti-TNF biologics showed lower neutralizing antibody titers against Alpha, Delta, and Gamma strains than every other group analyzed. <b>Conclusions:</b> IBD patients on anti-TNF drugs have a reduced serological response to the SARS-CoV-2 vaccine, with the Omicron variant not being neutralized. This highlights the necessity for tailored vaccine strategies for these patients.