This is a prospective, multicenter case-control study performed between September 2021 and March 2022 in the Pediatric Nephrology Units of IU- Cerrahpaşa School of Medicine, Memorial Hospital, Marmara University School of Medicine, IU- Istanbul School of Medicine, Medeniyet University School of Medicine, and Istinye University School of Medicine. The control group has consisted of age and gender comparable 19 healthy children without any acute infection or chronic disease, who were admitted to Cerrahpasa School of Medicine, Pediatric out-patient unit for routine control.
When permitted by local guidelines, children and adolescents who were over 12 years old were notified of vaccine eligibility and encouraged to schedule an appointment. The SARS-CoV-2 mRNA BNT162b2 vaccine (Pfizer-BioNTech®) administered to all participants by intramuscular route in the deltoid region. At least one month after the second dose of the vaccine, serum samples and whole blood samples were collected from all patients and controls, to analyze the humoral and cellular immune response to the vaccine. All samples were stored at -20 ◦C until testing. SARS-CoV-2 PCR test results were recorded retrospectively to determine natural infection.