In the case of IgM, a positive antibodies test occurred significantly often in females (OR = 1.31; 1.003–1.732), in older age (OR = 1.02; 1.01–1.03), in overweight or obese people (OR = 1.46; 1.11–1.95), and in people with previous COVID-19 contact or quarantine (OR = 1.92, 1.48–2.49). This evidence concerns the gene CD40LG and COVID-19.