IL4 and pertussis: Three inflammatory cytokines were found to have a causal relationship with pertussis: IL-4 (OR = 0.3688, 95% CI = 0.16571–0.8208, P = .0145418), IL-18R1 (OR = 1.2757, 95% CI = 1.0499–1.5501, P = .0143), and FGF-21 (OR = 2.0747, 95% CI = 1.0669–4.0341, P = .03147).