NOS3 and COVID-19: 27-bp VNTR 4b/a) in 180 COVID-19 patients and found no statistically significant associations with disease severity overall. However, in a subgroup of patients under 50 years old without COPD, there was a trend toward increased frequency of the 4b/4b genotype and 4b allele among severe cases, suggesting a possible role of NOS3 genetic variants in younger individuals’ susceptibility to severe COVID-19 (İdikut et al., 2025)(Turkey, 180, 180, N/A)