acute kidney failure; child; clinical assessment; cold ischemia time; conference abstract; controlled study; coronavirus disease 2019; creatinine blood level; diuresis; drug combination; drug therapy; estimated glomerular filtration rate; female; graft failure; heart death; high risk population; human; human cell; human tissue; immunosuppressive treatment; incidence; kidney graft; leukopenia; lymphocyte; major clinical study; male; mortality; nephrotoxicity; neutropenia; outcome assessment; retrospective study; surgery; viremia; belatacept; mycophenolic acid; steroid