Key words : Children, Immunosuppression, Kidney transplant, SARS-CoV-2

Introduction
After the outbreaks of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2003 and the Middle East respiratory syndrome-related coronavirus (MERS-CoV) in 2012, the world is now facing a third rapidly spreading coronavirus outbreak caused by SARS-CoV-2.^1-3 Coronavirus disease 2019 (COVID-19) was declared a global pandemic by the World Health Organization.⁴ COVID-19 first appeared in Turkey in March 2020; it spread rapidly and caused over 50 thousand deaths to date.

Although it is primarily a respiratory disease, there is a wide range of presentations, from mild symptoms (including headaches, anosmia, myalgias, sore throat, emesis, and diarrhea) to devastating respiratory failure, multiorgan insufficiency, and even death.⁵ Up to now, we have observed that COVID-19 causes less symptoms in healthy children than in adults and that most children survive asymptomatically. However, there is insufficient evidence to determine whether a similar benefit exists in pediatric kidney transplant recipients or children with chronic diseases. COVID-19 may present with unusual symptoms in immunocompromised people. Immunocompromised adults, including solid-organ transplant recipients, have been observed to be at an increased risk.^6-8 A multicenter study of over 100 adult kidney transplant recipients revealed a 32% mortality rate.⁹ However, few studies on pediatric transplant recipients have been published, and it is unknown whether their clinical course is more like that of adult transplant patients or is more similar to healthy age-matched pediatric populations. It is still unknown which risk factors contribute to the severity of the disease and what individual factors lead to mild versus severe disease. The purpose of this article was to provide our findings regarding COVID-19 infection in pediatric kidney transplant recipients at the Başkent University Transplantation Center.

Materials and Methods
Between March 2020 (the date of the first case in Turkey) and October 2021, we collected data on COVID-19 cases in kidney transplant recipients under the age of 20 years who were followed at the Başkent University Transplantation Center. COVID-19 tests were conducted in patients who had a history of close contact and/or unsafe interactions with COVID-19 or who had at least one of the disease symptoms (fever, cough, loss of smell, respiratory signs, and diarrhea). The polymerase chain reaction (PCR) method was used to examine combined throat and nasal swab samples taken twice within a 24-hour interval.

In accordance with our hospital procedure, we also administered routine COVID-19 PCR tests for patients prior to hospitalization or any surgical intervention. In addition to patients who presented with symptoms and had possible contacts with COVID-19, all patients who tested positive for COVID-19 by PCR during routine evaluation were further evaluated.

Patients who showed clinical symptoms or had suspected contact but received negative initial PCR results underwent COVID-19 immunoglobulin M (IgM) and immunoglobulin G (IgG) level examinations and received a second PCR test at least 24 hours later. Our study included patients who tested positive for the COVID-19 antibody or PCR tests.

For analyses, we reviewed patient demographic characteristics, date of transplant, duration of follow-up posttransplant, detailed clinical signs and symptoms, status of respiratory and renal involvement, immunosuppressive regimens used, and clinical outcomes.

Statistical analyses
The IBM SPSS statistics program (version 24) was used for statistical analysis. For categorical variables, descriptive statistics are presented as numbers and percentages, whereas continuous variables are presented as mean, standard deviation, median, minimum, and maximum.

Results

Between March 2020 and October 2021, 23 of 215 pediatric kidney transplant recipients who were actively followed at our center were determined to be positive for COVID-19. Suspected contact was discovered in 12 of the 23 patients included in the study. Nine patients were diagnosed based on the results of PCR or antibody tests performed due to the presence of symptoms without a previous contact with COVID-19. Two patients were diagnosed incidentally because of standard COVID-19 screening performed prior to hospitalization.

There were an additional 19 patients who had close contact with confirmed cases of COVID-19 (mainly familial contact); however, IgM and IgG levels for COVID-19 were negative, and PCR tests were negative at least twice. The clinical findings of these 19 patients were closely followed for 14 days, and no signs associated with transmission were observed. These patients were excluded from the study due to the absence of evidence of disease.

Among pediatric kidney transplant recipients at our center, COVID-19 infection occurred in 10.7% (n = 23 patients). The mean age of the 23 patients was 14.6 ± 4.7, and 9 were female patients. The mean follow-up time posttransplant was 52.3 ± 43.2 months. In 13 patients (56.5%), fever was the most frequent symptom. Nine patients (47%) had mild symptoms (without fever), such as rhinorrhea, sore throat, cough, loss of smell and taste, back pain, and muscle pain. Most patients (n = 18, 78%) had minor symptoms and recovered completely after receiving supportive treatment (antipyretics, vitamins, oral hydration). Four patients developed acute kidney injury. Three patients recovered completely following fluid replacement therapy. Four patients (17%) required hospitalization, and their details are described below. Immunosuppressive treatment was reduced in all our renal transplant patients with confirmed COVID-19 infection. One patient (4.3%) died because of COVID-19-associated acute respiratory and multiorgan failure. Our mortality rate was determined to be 4.3%. Table 1 presents the demographic and clinical features of the study patients.

First hospitalized patient
A 16-year-old female patient presented with cough, fever, and chest pain. She had a transplant from a living donor in December 2016 and was receiving tacrolimus, mycophenolate mofetil, and low-dose prednisone. The patient was diagnosed with COVID-19 infection shortly after receiving acute antibody-mediated rejection treatment with plasmapheresis (daily, 5 sessions), intravenous immunoglobulin (IVIg; 2g/kg), and rituximab (375 mg/m2, single dose). Immunosuppressive doses of mycophenolate mofetil were rapidly decreased. Her blood creatinine level was 2.8 mg/dL when acute antibody-mediated rejection was detected; 1 week later, her creatinine level increased to 4.5 mg/dL when COVID-19 disease was confirmed. She was intubated on day 5 of hospitalization due to increased difficulty breathing and decreasing oxygen saturation in the intensive care unit. Her radiologic examination revealed a widespread ground-glass pattern on both lung sides. The patient died approximately 1 month after admission to the intensive care unit because of severe respiratory failure and multiorgan failure.

Second hospitalized patient
A 5-year-old female patient was admitted to the hospital with cough, headache, vomiting, and diarrhea. She had a diagnosis of end-stage renal disease due to cystinosis. Her respiratory findings did not progress. She was treated with antibiotics and intravenous fluids. She was discharged from the hospital following a short hospitalization.

Third hospitalized patient
A 15-year-old male patient was admitted to the hospital with fever, cough, muscle pain, and shortness of breath. He had chronic antibody-mediated rejection and was treated with prednisolone and IVIg. His radiologic examination showed bilateral viral pneumonia with ground-glass pattern. Although the patient developed pneumonia, he did not require intubation and recovered completely after receiving antibiotics, antivirals (favipiravir), and supportive treatment (vitamins C and D).

Fourth hospitalized patient
A 17.5-year-old male patient presented with 2 days of lasting rhinorrhea, sore throat, cough, and fever to a maximum 38.5 °C. In March 2021, he received a kidney transplant from a living donor and was started on tacrolimus, mycophenolate mofetil, and low-dose prednisone. Respiratory symptoms did not worsen, and the patient reported feeling better. His fever decreased on day 4 of hospitalization. Creatinine concentration increased from 0.97 to 1.3 mg/dL. After a 5-day hospitalization, during which he was treated with intravenous fluid replacement, antipyretics, and antibiotics, he was discharged with no further symptoms.

Discussion
Because of the immunosuppressive nature of pediatric kidney transplant, these children are thought to be at risk of infections. When COVID-19 emerged in December 2019, we were confronted with an unpredictable and unknown disease. Additional research was required because the disease was shown to progress differently in different patients based on their age, concurrent illnesses, and immune system status. Numerous case reports and series have been published describing the clinical findings, treatments, outcomes, and mortality rates associated with COVID-19 in adult transplant recipients. Most investigations on the effects of COVID-19 on pediatric kidney transplant recipients, however, are case reports or small case series.

In most of our patients, we preferred the PCR test for diagnosis. Because kidney transplant recipients are immunosuppressed, there is debate over the sufficiency of the antibody response to COVID-19 infection in these patients.^10,11 With the limitations of antibody-based diagnostics, we have emphasized PCR testing over antibody measures for COVID-19 diagnosis. In addition, we only examine COVID-19 IgM and IgG antibodies in individuals with suspected exposure history, those with symptoms compatible with COVID-19, those with negative repeated PCR results, and those with no alternative viral etiology of the symptoms detected.

In the present study, COVID-19 infection occurred in 10.7% of our pediatric kidney transplant recipients. Although this was a small study, this rate reflected the disease prevalence in our country’s general population. However, 1 of 23 kidney transplant recipients died, resulting in a mortality rate (4.3%) that was much higher than that of the general Turkish population (range, 0.9%-1.1%). In the literature, COVID-19-related mortality in pediatric renal transplant recipients has been reported to be quite low. In addition, pediatric patients receiving immunosuppressive treatments for acute glomerular disease have been shown to have a higher mortality rate than transplant recipients. According to some research, death rates are particularly high in low-income societies, possibly due to the late detection of COVID-19 or insufficient treatment.^12,13 Four deaths were reported in a multicenter European study of 582 children from 21 different countries (mortality rate of 0.7%).¹² Another multicenter research with a similar patient population revealed 4 deaths among the 113 participants (mortality rate of 3.5%).¹³ Severe morbidity and mortality rates related to COVID-19 may be due to acute and high-dose immunosuppression rather than a mild chronic course.

Our observations of 23 pediatric transplant patients with COVID-19 infection indicated that symptoms were generally mild and behaved similarly to symptoms shown in the general population. In most of our patients, supportive care was sufficient, with 1 patient having poor prognosis. This patient received plasmapheresis, IVIg, and a single dose of rituximab for acute antibody-mediated rejection that occurred 4 years and 7 months after kidney transplant. One week later, respiratory distress due to COVID-19 emerged, requiring urgent mechanical ventilatory support. The patient died a few days later. She did not have any other comorbidities. We believe that the main factor contributing to this patient’s poor outcome was increased immunosuppression from rituximab. Nonetheless, there are studies in the literature that contradict this hypothesis. According to Sinha and colleagues, rituximab treatment had no statistically significant influence on COVID-19 infection-related hospitalization, need for respiratory support, or mortality.¹⁴ Despite most of our pediatric transplant recipients having mild symptoms of COVID 19, we believe that particular caution should be observed in patients who have recently received intensive immunosuppressive medication.

Nair and colleagues reported a 30% mortality rate and a 50% acute kidney injury rate in 10 adult transplant recipients with COVID-positive PCR tests.¹⁵ Another study examined 90 adult organ transplant recipients and reported that 30% had severe disease, with an 18% mortality rate. Although recipients of different organs were included in this study, it was highlighted that organ type was not a significant predictor of prognosis.¹⁶ Compared with adults, pediatric kidney transplant recipients have a significantly lower risk of severe disease and death. Among 1686 pediatric kidney transplant recipients analyzed in a multicenter study, 24 patients were found to be positive for COVID-19. According to this study, 25% of COVID-19-positive patients were found incidentally during screening tests of asymptomatic patients. Furthermore, this study reported no graft loss, respiratory failure, or death as a result of COVID-19 infection.¹⁷ International data have shown that COVID-19-related outcomes are similar in immunosuppressed versus nonimmunosuppressed children.18 D’Antiga concluded that immunosuppressed patients did not have an increased risk of developing severe pulmonary disease and that children under the age of 12 years did not get severe pneumonia regardless of their immunological status.¹⁹ Comorbidities such as advanced age, asthma, diabetes, and obesity have been reported to contribute to a higher severity of disease and a higher mortality rate among adult transplant recipients compared with pediatric transplant recipients.^15,20

We will probably continue to treat COVID-19 for a lengthy period. As a result of potential new vaccines, national immunization programs, and the emergence of novel virus strains, the clinical picture may change in the future. It is obvious that social distance and the use of masks will continue to be significant for a long period of time, particularly among certain patient groups, such as renal transplant recipients. We anticipate that, as our knowledge of long-term outcomes and potential complications improves, our approach to patients will evolve. We believe that, as information sharing increases, we will learn more about COVID-19 in renal transplant recipients.

References:

1. Tsang KW, Ho PL, Ooi GC, et al. A cluster of cases of severe acute respiratory syndrome in Hong Kong. N Engl J Med. 2003;348(20):1977-1985. doi:10.1056/NEJMoa030666
   CrossRef - PubMed
   
2. Zaki AM, van Boheemen S, Bestebroer TM, Osterhaus AD, Fouchier RA. Isolation of a novel coronavirus from a man with pneumonia in Saudi Arabia. N Engl J Med. 2012;367(19):1814-1820. doi:10.1056/NEJMoa1211721
   CrossRef - PubMed
   
3. Zhu N, Zhang D, Wang W, et al. A novel coronavirus from patients with pneumonia in China, 2019. N Engl J Med. 2020;382(8):727-733. doi:10.1056/NEJMoa2001017
   CrossRef - PubMed
   
4. Cucinotta D, Vanelli M. WHO declares COVID-19 a pandemic. Acta Biomed. 2020;91(1):157-160. doi:10.23750/abm.v91i1.9397
   CrossRef - PubMed
   
5. Yuki K, Fujiogi M, Koutsogiannaki S. COVID-19 pathophysiology: A review. Clin Immunol. 2020;215:108427. doi:10.1016/j.clim.2020.108427
   CrossRef - PubMed
   
6. Yi SG, Rogers AW, Saharia A, et al. Early experience with COVID-19 and solid organ transplantation at a US high-volume transplant center. Transplantation. 2020;104(11):2208-2214. doi:10.1097/TP.0000000000003339
   CrossRef - PubMed
   
7. Coll E, Fernández-Ruiz M, Sánchez-Álvarez JE. COVID-19 in transplant recipients: The Spanish experience. Am J Transplant. 2021;21(5):1825-1837. doi:10.1111/ajt.16369
   CrossRef - PubMed
   
8. Fernandez-Ruiz M, Andres A, Loinaz C, et al. COVID-19 in solid organ transplant recipients: A single-center case series from Spain. Am J Transplant. 2020;20(7):1849-1858. doi:10.1111/ajt.15929
   CrossRef - PubMed
   
9. Cravedi P, Mothi SS, Azzi Y, et al. COVID-19 and kidney transplantation: Results from the TANGO International Transplant Consortium. Am J Transplant. 2020;20(11):3140-3148. doi:10.1111/ajt.16185
   CrossRef - PubMed
   
10. Wang AX, Quintero Cardona O, Ho DY, Busque S, Lenihan CR. Influence of immunosuppression on seroconversion against SARS-CoV-2 in two kidney transplant recipients. Transpl Infect Dis. 2021;23(1):e13423. doi:10.1111/tid.13423
    CrossRef - PubMed
    
11. Xia Z, Liu X, Hu X, et al. Failed antibody response in a renal transplant recipient with SARS-CoV-2 infected. Transpl Infect Dis. 2020;22(5):e13349. doi:10.1111/tid.13349
    CrossRef - PubMed
    
12. Gotzinger F, Santiago-Garcia B, Noguera-Julian A, et al. COVID-19 in children and adolescents in Europe: a multinational, multicentre cohort study. Lancet Child Adolesc Health. 2020;4(9):653-661. doi:10.1016/S2352-4642(20)30177-2
    CrossRef - PubMed
    
13. Marlais M, Wlodkowski T, Al-Akash S, et al. COVID-19 in children treated with immunosuppressive medication for kidney diseases. Arch Dis Child. 2020;106(8):798-801. doi:10.1136/archdischild-2020-320616
    CrossRef - PubMed
    
14. Sinha R, Marlais M, Sarkar S, et al. Impact of COVID-19 pandemic on use of rituximab among children with difficult nephrotic syndrome. Pediatr Res. 2021;1-3. doi:10.1038/s41390-021-01744-8
    CrossRef - PubMed
    
15. Nair V, Jandovitz N, Hirsch JS, et al. COVID-19 in kidney transplant recipients. Am J Transplant. 2020;20(7):1819-1825. doi:10.1111/ajt.15967
    CrossRef - PubMed
    
16. Pereira MR, Mohan S, Cohen DJ, et al. COVID-19 in solid organ transplant recipients: Initial report from the US epicenter. Am J Transplant. 2020;20(7):1800-1808. doi:10.1111/ajt.15941
    CrossRef - PubMed
    
17. Varnell C, Jr., Harshman LA, Smith L, et al. COVID-19 in pediatric kidney transplantation: The Improving Renal Outcomes Collaborative. Am J Transplant. 2021;21(8):2740-2748. doi:10.1111/ajt.16501
    CrossRef - PubMed
    
18. Marlais M, Wlodkowski T, Vivarelli M, et al. The severity of COVID-19 in children on immunosuppressive medication. Lancet Child Adolesc Health. 2020;4(7):e17-e18. doi:10.1016/S2352-4642(20)30145-0
    CrossRef - PubMed
    
19. D'Antiga L. Coronaviruses and immunosuppressed patients: the facts during the third epidemic. Liver Transpl. 2020;26(6):832-834. doi:10.1002/lt.25756
    CrossRef - PubMed
    
20. Elias M, Pievani D, Randoux C, et al. COVID-19 Infection in kidney transplant recipients: disease incidence and clinical outcomes. J Am Soc Nephrol. 2020;31(10):2413-2423. doi:10.1681/ASN.2020050639
    CrossRef - PubMed