Similarly, abroad imported case (HR 5.152, 95% CI 1.936–13.711, P = 0.001), involvement in a cluster (HR 0.365, 95% CI 0.180–0.743, P = 0.005), any symptom during the acute phase of Covid-19 (HR 0.368, 95% CI 0.161–0.842, P = 0.018), and pneumonia (HR 0.477, 95% CI 0.261–0.873, P = 0.016) were significantly associated with IgM seroconversion time. This evidence concerns the gene CD40LG and pneumonia.