Another interesting field for further exploration of GDF-15 is in patients with low seropositivity after COVID-19 vaccination, as described in a systematic review by Kyuyeon Cho et al. Low seropositivity is often found in patients with weakened immunity due to comorbidities, and an adequate biomarker to differentiate such patients in the general population has yet to be found [39]. This evidence concerns the gene GDF15 and COVID-19.