In order to compare the infection situation between the KTRs and the non-KTRs groups, we conducted a case-control study. Because of the sudden onset and rapid infection of COVID-19, we did not have enough time to prepare for a prospective study. However, we collected a large number of cases, which can also accurately explain the problem.
According to our results, there was no statistical difference in the age and gender composition of the patients in the renal transplant group compared with those in the non-transplant group. While there was a difference in vaccination between the two groups, with the vaccination rate in the general population being 67.2%, significantly higher than in the renal transplant group (P < 0.05)(Table 1). The difference in vaccination may be one of the reasons of the different complications between the kidney transplant group and the general population group, which also indicates the protective effect of vaccination. As for the general population, the reason for the complications of the non-KTRs group may be that our non-KTRs group is not the general population in general sense, but the people who need to be hospitalized after COVID-19 infection, which is the general population relative to the transplant population. Therefore, our general population group will also have complications.
According to early data from Spain (as of December 2019), it occurs within 60 days after kidney transplantation 46% of patients infected with COVID-19 died[20]. The early symptoms of the solid organ transplantation recipients were concealed due to the use of immunosuppressants, but the later disease progressed rapidly. For example, the incidence of pneumonia, the proportion of transfer to intensive care unit (ICU), and the mortality rate of the solid organ transplantation recipients recipients were increased compared with other COVID-19 infected patients [21]. Among hospitalized recipients of KTRs, the risk of secondary acute kidney injury and dyspnea is 3.78 times and 4.53 times higher than that of normal individuals, respectively, indicating poor prognosis [22].
As shown in Fig. 2, there was no difference in the incidence of fever between the two groups, while the highest temperature and the number of days of fever of the two groups are different. The average highest fever temperature of the non-KTRs group is 38.87℃, slightly higher than that in the KTRs group (38.87℃). There is also a difference in absolute lymphocyte count between the two groups. The absolute lymphocyte count of the kidney transplant population at admission and 7 days after admission is lower than that of the general population, with a statistically significant difference (P < 0.001, P < 0.001). The lymphocyte count of the kidney transplant population is also lower than that of the general population, and the difference is statistically significant (P < 001). This may be related to the use of immunosuppressants by patients after transplantation.
Due to the use of immunosuppressants, it is difficult for renal transplant recipients to carry out immunotherapy for COVID-19 infection and inflammatory reaction. Monovir is less effective compared to other recommended antiviral drugs, so it is not a first-line recommended medication for the general population. However, this drug is not as effective as solid organ transplant recipients. There was no significant interaction between the immunosuppressive drugs used by the recipient in solid organ transplant recipients[13].
According to the Diagnosis and Treatment scheme of COVID-19 (Version X) of China, the patients infected with Omicron were clinically classified to mild, moderate, severe and critically ill. The first two types, collectively referred to as ordinary patients, were recommended to stay at home and take self isolation and monitoring. Whlie in terms of those with high-risk factors, they were suggested to take antiviral treatment as soon as possible. Most KTRs have 2–3 high-risk factors, which belong to the category of high risk groups that exhibit severe or critically severe conditions. So the antiviral treatment is crucial, as well as the monitoring and maintenance of graft function[2].
Our results indicate that the use of intravenous corticosteroids is significantly higher than that of the general population (42.8% vs 6.0%, p = 0.000), and the use of small molecule drugs such as azivudine and combination packaging of nimatevir/ritonavir tablets is also significantly higher than that of the general population. The use of monoclonal antibodies and gamma globulin is also higher than that of the general population.
According to Table 2, the time from symptom onset to discharge in KTRs is significantly longer than that of the general population, with statistical significance (p = 0.000). The incubation period of solid organ transplant recipients infected with COVID-19 is 1–14 days, most of them are 3–7 days, and the incubation period is infectious. At present, there is no evidence showed that there is difference between the latency of transplant patients and other COVID-19 infected patients [23]. Typically, the median detoxification period for individuals infected with the Omicron variant is 11.3 days, while for the solid organ transplant recipients, it is extended to 14 days[24].