Authors' reply: the biologic importance of the vitamin D binding protein polymorphism in pediatric COVID-19 patients.

What is Known? • Vitamin D has multiple roles in the immune system that can modulate the body reaction to an infection • Vitamin D binding protein (DBP) is the key transport protein which, along with albumin, binds over 99% of the circulating vitamin D metabolites What is New? • Lower 25 OH vitamin D levels were associated with higher inflammation markers, suggesting an important role of vitamin D in the clinical course of COVID-19 in children and adolescents probably by regulating the systemic inflammatory response • Further studies are warranted to investigate the possible causal association of DBP levels and polymorphism with vitamin D status (total and bioavailable vitamin D) in COVID-19 patients.

Demographic and Clinical Characteristics of COVID-19 in Children and the Effect of Household Tobacco Smoke Exposure on COVID-19.

OBJECTIVE: Environmental tobacco smoke (ETS) exposure is associated with many diseases, including lower respiratory tract infections, in pediatric age groups. In this study, we aimed to assess the effect of household ETS exposure on symptom frequency and clinical severity in children and adolescents with COVID-19. MATERIALS AND METHODS: This retrospective study included pediatric cases (<18 years old) with a positive SARS-CoV-2 test, who were admitted to our hospital between 20.03.2020 and 01.05.2020. Patients with respiratory diseases and active smokers were excluded. Demographic characteristics, symptoms, and clinical severity of COVID-19 were obtained from parents and children using a questionnaire and from patients' files. Household ETS exposure was assessed by questionnaire. RESULTS: A total of 167 patients (median age 145 months, 50.7 % male) were included in the study. The frequency of household ETS exposure was 50.9%, and the frequency of cough was significantly higher in exposed children than non-exposed children (71.4% vs 50.8% respectively, p=0.02). The frequency of both fever and cough was significantly higher ETS-exposed in the subgroup of cases with a mild clinical course (69.5% vs 48.1% respectively, p= 0.02 for fever and 67.8% vs 44.4% respectively, p=0.01 for cough). There was no relationship between clinical severity and household ETS exposure. CONCLUSION: Household ETS exposure may impact COVID-19 pediatric cases as demonstrated by the increased frequency of cough and fever in ETS-exposed children. As new lockdown measures are implemented, increasing public awareness about the effect of household ETS exposure on COVID-19as well as encouraging a decrease in ETS exposure are essential.