Even though most participants (58.0%; n = 232/400) had previously had symptoms similar to COVID-19, 86.6% (n = 201/232) and 27.2% (n = 63/232) of them were negative for anti-SARS-CoV-2 IgM and anti-SARS-CoV-2 IgG, respectively. Here, CD40LG is linked to COVID-19.