Introduction: Renal transplant patients develop a decreased antibody response to COVID‑19 vaccines compared to patients on dialysis. Antibody titers are expected to decline over time.  There is little information on the behavior of these titers in patients with a significant immunosuppressive load, such as transplant recipients. This paper aims at describing the behavior of anti-SARS-Cov-2 antibodies in a group of patients vaccinated while on dialysis who received a kidney transplant, and at comparing them with a group of patients who continued on hemodialysis.

Methods: For dialysis patients receiving a deceased donor kidney, on the transplantation day and before starting the immunosuppressive therapy, anti-SARS-CoV-2 antibodies were measured and measured once again 2 months after transplantation on average. Patients who were and continue to be on hemodialysis were used as a control group. Their antibodies were measured at the same moments as those for transplant recipients.

Results: Sixteen patients were evaluated, 8 were renal transplant patients (RTPs) and 8 were patients on dialysis (HDPs). The gender distribution was 13 men in total (7 RTPs and 6 HDPs). Average age was 42±14 and the length of time on dialysis for RTPs was 4.8±3 years, with no difference between RTPs and HDPs. In RTPs, baseline antibodies were first measured (prior to transplantation) 97 days (69-133) after the second dose and were measured once again 76 days (44-103) after transplantation, i.e. 173 days after the second dose and 28 days after the third dose. In the HD group, baseline antibodies were measured 40 days after the second dose and were measured once again 120 days after the second dose and 84 days after the third one. In RTPs antibody titers were 3.61±0.25 prior to transplantation and 3.12±1.2 following transplantation, with no significant differences between the pre- and post-transplant periods (p=0.3). It should be noted that 5 out of the 8 patients had received a third dose of the vaccine. In HDPs, no significant differences were found either when comparing the titers of baseline antibodies and those of the second measurement (3.37±0.02 vs. 3.64±1.2 P=0.5). When comparing the antibody variation in the first and second measurements, a decline of 0.05±1.84 in RTPs and an increase of 0.26±1.2 in HDPs were found, with no statistically significant differences. All RTPs have a stable kidney function and do not require dialysis.

Conclusion: While RTPs showed a decline in antibody titers and HDPs, a slight increase in titers, no differences between baseline and subsequent determinations or between both groups were found. Further studies are required to assess the effects of immunosuppression and whether it makes this population more susceptible to SARS-CoV-2 infection.