In this research, changes in absorbance in the areas related to IgG (1560–1464 cm−1), IgM (1420–1289 cm−1, 1160–1028 cm−1), and IgA (1285–1237 cm−1) were observed, noticing a higher absorbance in the spectra of COVID-19 group, which is concordant with all those mentioned above. Here, CD40LG is linked to COVID-19.