*Purpose: COVID-19 poses a disproportionate threat to renal transplant recipients (RTR), who are chronically immunosuppressed. Studies have indicated a 16% mortality rate compared to <5% for the general population. Effective vaccines (Pfizer, Moderna and, Johnson & Johnson) provided hope for protection against severe COVID-19 in this at-risk population. However, based on experience with vaccines against other viral infections, two primary concerns arose: 1) would the SARS-CoV-2 vaccines be effective in this population; 2) could these vaccines provoke rejection?

*Methods: To address these questions, we tested serum creatinine, anti-SARS-CoV-2 S antibody (Roche Elecsys^R), Donor Specific anti HLA Antibodies, other antibodies against SARS-CoV-2, other coronaviruses (LABScreenTMCOVID Plus, One Lambda), and donor derived cell free DNA (dd-cfDNA; fraction, absolute and total quantity, using the Prospera^TM Test, Natera, Inc.) in RTR at the time of vaccine doses 1 and 2 and 1, 3, and 6 months after the second dose. dd-cfDNA ≥1% and 78 cp/mL indicated an increased risk of rejection. 53 patients were consented and enrolled in the study. This study received IRB approval. Statistical analysis was performed using paired two-tailed student’s t-test.

*Results: This preliminary analysis analyzed the impact of vaccination on dd-cfDNA levels in 31 RTR patients. This cohort was primarily female (67%) and of hispanic descent (48.3%) with a median age 55 years (range: 19-81). All but 1 patient received the Pfizer vaccination series. Mean time from transplant to vaccination 1 was 114.6 months (range: 10-359 months). Between vaccination 1 and 2, no patients had clinical suspicion of rejection, were hospitalized or underwent for-cause biopsy. No significant differences in dd-cfDNA or total cf-DNA levels were found by Prospera testing between vaccination 1 and 2. (Table 1). Between vaccination 1 and 2, one patient had an increase dd-cfDNA% above the normal range (0.14%, 2.37%), but absolute dd-cfDNA quantity remained in normal range (13.70 cp/mL, 66.08 cp/mL). At the time of the vaccination 1, dd-cfDNA% was elevated in 2 patients. At vaccination 2, dd-cfDNA% had returned to the normal range for one patient (dd-cfDNA quantity was normal for both vaccinations), while both dd-cfDNA% and quantity remained elevated in the other.

*Conclusions: Based on measurement of dd-cfDNA fraction, absolute quantity and total quantity with the Prospera test at vaccination 1 and 2, there was no evidence of SARS-CoV-2 vaccination-induced rejection.

« Back to 2022 American Transplant Congress