PhD student Department of Biohealth Regulatory Science, Sungkyunkwan University, Suwon, South Korea, Republic of Korea
Background: Chronic Kidney Disease (CKD) patients were given priority to Covid-19 vaccination, since CKD is a key risk factor for severe Covid-19. Despite this, vaccine hesitancy was reported among these patients, possibly due to limited evidence of Covid-19 vaccine efficacy specifically for overall CKD patients regardless of dialysis status.
Objectives: To evaluate the effectiveness of Covid-19 vaccine in CKD patients by assessing severe clinical outcomes after Covid-19 infection.
Methods: A retrospective cohort study was conducted by using the Korean nationwide Covid-19 registry linked with claims data. The study cohort included CKD patients who were diagnosed with Covid-19 between January 2020 and November 2021. We compared the vaccinated group to the unvaccinated, with the primary study outcome being all-cause death and the secondary outcome being emergency department visits and all-cause hospitalization, all followed up for 28 days after the Covid-19 infection date. As a subgroup analysis, we further assessed the risk by age, sex, Charlson Comorbidity Index (CCI) score, and status of dialysis. Hazard ratios (HRs) for each outcome were estimated using the Cox proportion hazard model, while adjusting for age, sex, comorbidities, and dialysis status. Additionally, we evaluated which factors were associated with the primary outcome, all-cause mortality after Covid-19 infection, in patients with CKD.
Results: We identified 1,321 Covid-19 infected CKD patients, of whom 682 were vaccinated [age, mean (SD) = 68.0 (13.4); 61.6% males, 11.1% on dialysis], and 639 were unvaccinated [age, mean (SD) = 63.1 (16.4); 57.8% males, 15.7% on dialysis]. Compared to unvaccinated CKD patients, the risk of all-cause death (aHR: 0.63; 95% CI: 0.44-0.91) and emergency department visits (0.62; 0.45-0.87) after Covid-19 infection were lower in vaccinated group, while no significant difference in all-cause hospitalization was observed (0.91; 0.75-1.10). Subgroup analysis did not reveal any differences in the risk by age, sex, CCI, and dialysis status. In the analysis of evaluating the variables relevant to severe clinical outcomes after Covid-19 infection, age (1.10; 1.07-1.12), CCI (1.28; 1.12-1.46), and status of dialysis (1.63; 1.01-2.62) were found to be significantly associated with a higher risk of death in patients with CKD.
Conclusions: Covid-19 vaccination was associated with a reduced risk of mortality and emergency department visits in CKD patients after Covid-19 infection. In addition, older age, having higher comorbidities, and undergoing dialysis were observed as risk factors for death after Covid-19 infection. Overall, these findings will assist clinicians and CKD patients in their decision-making regarding Covid-19 vaccination during the ongoing pandemic.
