Nucleic acid negative IgM positivity may be due to the fact that the organism is in the midst of a viral infection, but the virus was not collected during sampling for nucleic acid testing, resulting in nucleic acid negativity, or it may be due to recent vaccinations. IgM is an immunoglobulin, and IgM positivity occurs in the early stages of the organism’s infection, and as the disease progresses and the virus is gradually cleared, the protective antibody IgG appears. When the organism is IgM-positive, it means that the organism is in the acute phase of the disease, and at this time, the negative nucleic acid test may be due to the low viral load in the early stage of the disease, and the nucleic acid sampling failed to accurately collect the virus, so the nucleic acid test is negative. Repeat testing is recommended to determine the current infection status of the organism in the event of a negative nucleic acid IgM positive test due to the possibility of testing error. Nucleic acid-negative IgM positivity can also be caused by recent vaccination, which is due to the vaccine stimulating the body’s immune system to produce antibodies without the body itself becoming infected.