Lifestyle & Biochemical Parameters that May Hamper Immune Responses in Pediatric Patients After Immunization with the BNT162b2 mRNA COVID-19 Vaccine

Background: The aim of the study is to evaluate whether increased Body Mass Index (BMI), biochemical and lifestyle parameters linked to obesity and smoke exposure disrupt immune responses of children and adolescents following vaccination with the mRNA BNT162b2 vaccine. Methods: Participants were assigned to receive two doses of the mRNA vaccine. Anti-SARS-CoV-2 IgG and neutralizing antibodies (abs) were measured before vaccination (T0) and 14 days after the second dose (T1). BMI and biochemical parameters were evaluated at T0. A questionnaire on lifestyle characteristics was filled in. Results: IgG Optical Density (OD) ratio at T1 was lower in the overweight-obese group regardless of COVID-19 disease positive history [p=0.028 for the seronegative group, p=0.032 for the seropositive group]. Neutralizing abs were lower in overweightobese participants in the seronegative group at T1 [p=0.008]. HDL, Fasting Glucose/insulin Ratio (FGIR), C-Reactive Protein (CRP), HBA1c, uric acid and smoke exposure were significantly correlated with BMI [p=0.006, p<0.001, p<0.001, p=0.006, p=0.009, p<0.001, respectively]. The main biochemical parameters that were inversely correlated with IgG and neutralizing titers at T1 were uric acid [p=0.018, p=0.002], FGIR [p=0.001, p=0.008] and HBA1C [p=0.027, p=0.038], while smoke exposure negatively affected the humoral immune responses at T0 in the convalescent group [p=0.004, p=0.005]. Conclusions: Current data suggests that uric acid, Insulin Resistance (IR) and smoke exposure could adversely affect the immune responses in overweight-obese vaccinated children highlighting the need for actions needed for better protection of this specific subgroup.