To the Editor:

We are writing in reference to the publication on “Predictors of moderate, severe, and critical COVID-19 infection in a largely vaccinated kidney transplant recipient cohort during the Omicron era: the importance of timely booster vaccinations and early presentation to care [1].” This single-center retrospective analysis sheds light on the factors that influence the severity of coronavirus disease 2019 (COVID-19) in kidney transplant recipients (KTRs), who are considered a high-risk population. However, there are a few flaws in this study that require more investigation. One limitation is the retrospective design, which fundamentally limits the ability to discern causal linkages. The study is mostly based on existing data, which makes it dependent on the accuracy and completeness of the obtained information. Furthermore, the study observed that greater age and longer duration of symptoms were associated with increased severity; however, the study did not investigate other potentially critical variables, such as comorbidities and immunosuppressive medication therapy. These factors may also impact the severity of disease in the KTR group.

The sample size of moderately to severely unwell individuals (49 of 603 infected patients) was modest, perhaps limiting the strength of some findings. Multivariate analysis was used in this investigation to account for confounding factors; nevertheless, the small number of patients with severe symptoms may impair the accuracy of the adjusted odds ratio, particularly for factors such as age and glomerular filtration rate. Further studies with larger sample sizes are required, ideally across multiple sites, are required. This may produce more robust results. Additionally, this study did not explore how KTRs' vaccination status (e.g., number of immunizations and booster vaccine duration) interacts with baseline immunosuppressive therapy to reduce the likelihood of catastrophic outcomes. To address this gap, future studies could consider implementing a longitudinal design to track vaccination and immunosuppressive medication regiments in real time. Moreover, incorporating a diverse range of transplant centers would provide more representative data on the variability of immunosuppressive therapy protocols across different healthcare settings.

A significant area for further discussion is how different immunosuppressive treatment regimens may interact with COVID-19 vaccinations and influence the course of infection. As recipients frequently use immunosuppressant medications, differing treatment regimens may affect their ability to amount on effective immune response to both immunization and infection. Another important question is whether the findings from KTR can be applied to other immunocompromised populations, such as those with autoimmune illnesses or undergoing chemotherapy.

A multicenter cohort study with a greater number of participants would allow for a more in-depth examination of the factors determining the severity of COVID-19. Furthermore, long-term outcomes of COVID-19 in recipients, particularly complications following the acute phase, should be investigated. Investigating the link between vaccination status and immune function would also be valuable. Furthermore, including information on the specific immunotherapy used in the sample group may help elucidate the impact of different treatment regimens on COVID-19 outcomes and the efficacy of vaccination in immunocompromised individuals.

No potential conflict of interest relevant to this article was reported.

All the work was done by Hinpetch Daungsupawong and Viroj Wiwanitkit. All authors read and approved the final manuscript.