RT-PCR positivity is a proxy for the expected presence of antibody, but negative antibody tests in RT-PCR-positive individuals could either reflect antibody test performance, or alternatively be explained by a failure to mount a measurable systemic IgM or IgG antibody response (eg, in cases of immunocompromised individuals), effective infection clearance through other immune mechanisms (eg, T cells), an issue with the sample (eg, a major interferent), or through a false-positive RT-PCR test in individuals who have not had SARS-CoV-2 infection. This evidence concerns the gene CD40LG and infection.