In patients with IBD who had received low accumulated dosages of anti-TNF-α agents, risks for pneumonia (HR = 2.2, 95% CI: 1.1–4.5), urinary tract infection (HR = 2.4, 95% CI: 1.3–4.5), sepsis (HR = 4.0, 95% CI: 2.6–6.1), and abdominal abscess (HR = 6.0, 95% CI: 3.4–10.5) increased. This evidence concerns the gene TNF and abdominal abscess.