Numerous studies have highlighted the importance of IgG as a biomarker for various pathological conditions. For instance, the outbreak of SARS-CoV-2 has once again brought attention to IgG serum levels as they fluctuate upon infection. Sun et al. investigated the response of IgG and IgM glycoproteins in COVID-19 patients and found elevated levels of N and S protein-specific IgG and IgM after the onset of symptoms in non-ICU patients. While serological methods cannot be used in the initial stages of infection, they can diagnose the disease in later stages. Hence, IgG can be used to identify people who have had the disease without showing symptoms. Hou et al. reported that quantifying IgG antibodies could be a useful tool to assess the prognosis and severity of COVID-19 infection. Zhang et al. suggested that immune response isotyping based on IgG response and NLR could help differentiate COVID-19 patients based on disease severity. In conclusion, IgG is a vital biomarker associated with various diseases. It plays a crucial role in humoral immunity and diversifies its capabilities to combat pathogens by binding to a diverse range of molecules. With advancements in serological tests, IgG has become an important tool for diagnosis, prognosis, and evaluation of disease severity, and its significance in vaccine development and biosensing cannot be overlooked.