Regarding IgA responses and neutralizing antibody responses, they were quite similar to those evidenced in healthy subjects in patients treated with vedolizumab or infliximab monotherapy but were significantly lower in those given the infliximab/thiopurine combination [50 The poor presence of neutralizing antibodies in patients receiving combined therapy could explain why patients with IBD receiving this treatment were found to be at increased risk of severe COVID-19 than those given monotherapy (51, 52). This evidence concerns the gene CD79A and inflammatory bowel disease.