Introduction

Coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 impacted the global health system in an unprecedented way. The rapid development of various vaccines has become an important milestone in combating the pandemic. Vaccination relies on the production of antibodies via stimulation of humoral immunity. However, data regarding antibody response to infection in immunosuppressed patients, including kidney transplant recipients, is not well defined.
Different mortality rates for COVID-19 were reported from different countries. According to a recent study in western countries, mortality rates changed between 4.0% and 16.1% for reported cases. Higher mortality rates were reported in patients with kidney disease, specifically, in patients with kidney transplantation mortality ranging between 18.0- 41.6% was reported in different studies [1-6]. Moreover, data on the seropositivity rate following COVID-19 in kidney transplant recipients are scarce and not in agreement across studies. According to a recent study, lower antibody response rates (41.0%) were reported in kidney transplant recipients following recovery from the infection [7,8]. On the other hand, Azzi et al. investigated 69 kidney transplant recipients with reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed COVID-19 infection, and they found anti-nucleocapsid antibodies in 55 (80.0%) of them [9].
Usually, higher antibody response rates were reported for patients from the general population [8]. In a recent study, anti-nucleoprotein seropositivity was found as 78.2% among health care workers with RT-PCR confirmed COVID-19 [10].
In this cross-sectional study, we aimed first to investigate the prevalence of anti–SARS-CoV-2 antibodies in kidney transplant recipients; secondly, we examined the factors associated with the absence of antibody response.