IL6 and susceptibility to pneumonia measurement: In our pooled analyses, IL-6 was significantly higher in COVID-19 patients with pneumonia compared to those without pneumonia (SMD = 0.34, 95% CI 0.17–0.52, p < 0.0001), and also higher in COVID-19 pneumonia cases compared to healthy controls (SMD = 0.49, 95% CI 0.31–0.68, p < 0.00001).