Background: COVID-19 caused by SARS-CoV-2 remains a major public health problem. Previous studies demonstrated that interferon lambda 4 (IFNL4) has antiviral activity against viral infections of the upper respiratory tract, including some coronaviruses. However, we have limited data about the association of these genetic variants with SARS-CoV-2 infection, especially among children with recurrent respiratory infections (RRI).

Objectives: The aim of this study was to identify a relationship between the ss469415590 polymorphism of gene IFNL4 and the severity of COVID-19.

Materials and methods: The study included 70 children with RRI, after laboratory-confirmed COVID-19. Patients were genotyped for IFNL4 ss469415590 and split the patients among two groups. Group 1 ? 28.6% (n=20) children with moderate COVID-19, group 2 ? 71.4% (n=30) with severe course of the disease.

Results: The presence of the CC allele of ss469415590 was significantly lower in group 2 compared to group 1 (38.6% vs 48.6%, p<0.001). These results were not affected by sex or age. The frequency of allele T was overexpressed in group 2 with regard to group 1 (80.0% versus 54.0%; p>0.05); OR=0.3 (CI 0.086-1).

Conclusions: Our study confirmed the association between the CC allele of ss469415590 and the course of COVID-19 among children with RRI, suggesting an important potential protective role for this genetic variant of IFNL4 in the prevention and prognosis of the disease.