By contrast, Guillain-Barre syndrome (GBS) (ROR 0.48, 95% CI 0.32–0.72) and non-infectious meningitis (ROR 0.5, 95% CI 0.29–0.86) were less frequently reported with anti-PD-1/PD-L1 compared with anti-CTLA4 monotherapy, and were more frequently associated with combination PD-1/PD-L1 + CTLA-4 blockade compared with monotherapy (ROR 2.0 [95% CI 1.2–3.1] and ROR 2.7 [95% CI 1.5–4.7] for GBS and meningitis, respectively). This evidence concerns the gene CTLA4 and infectious meningitis.