Background: The efficacy of SARS-CoV-2 vaccination among kidney transplant recipients (KTR) is low. The main goal of this study was to analyze factors that may influence the humoral response to vaccination. Methods: We analyzed the titer magnitude of IgG antibodies directed against spike (S)-SARS-CoV-2 antigen after the second dose of the mRNA vaccine in 142 infection naïve KTR (83 men, i.e., 58.4%) with a median age (IQR) of 54 (41–63), and 36 respective controls without chronic kidney disease. mRNA-1273 or BNT162b2 were applied in 26% and 74% of KTR, respectively. Results: S-specific immune response (seroconversion) was seen in 73 (51.41%) of KTR, and in all controls 36 (100%). Independent predictors of no response were elder age, shorter transplantation vintage, and a more than two-drug immunosuppressive protocol. In subgroup analyses, the seroconversion rate was highest among KTR without MMF/MPS treatment (70%), treated with no more than two immunosuppressants (69.2%), treated without corticosteroid (66.7%), younger patients aged <54 years (63.2%), and those vaccinated with the mRNA-1273 vaccine (62.16%). The independent predictors of higher S-antibody titer among responders were younger age, treatment with no more than two immunosuppressants, and the mRNA-1273 vaccination. Conclusions: Our study confirmed a low rate of seroconversion after vaccination with the mRNA vaccine in KTR. The major modifiable determinants of humoral response were the composition of the immunosuppressive protocol, as well as the type of vaccine. The latter could be taken into consideration when initial vaccination as well as booster vaccination is considered in KTR.

Introduction: The immune response to the primary (two-dose) series of mRNA COVID-19 vaccines in kidney transplant recipients (KTRs) is very weak. We conducted a longitudinal observational study to compare the humoral response to a third, additional primary dose of mRNA vaccines between infection-naïve (IN-KTRs) and previously infected KTRs (PI-KTRs). Methods: We measured the levels of anti-spike (anti-s) IgG antibodies before and 14–21 days after the third dose and, in the secondary analysis, we compared the antibody response to BNT162b2 versus mRNA-1273. The reactogenicity assessment included solicited local and systemic reactions. Results: A total of 112 KTRs were enrolled, including 83 IN-KTR and 29 PI-KTR, among whom seroconversion in anti-s antibodies after the primary two-dose vaccination was achieved in 45.78% and 100% of cases, respectively. After three months, a waning antibodies titer by 67.4% (IN-KTR) and 7.5% (PI-KTR) was observed. After the third dose of the mRNA vaccine, 71.08% (59/83) of IN-KTR and 96.5% (28/29) of PI-KTR samples were seroconverted with a median anti-s titer of 468.0 (195.0–1620.0) BAU/mL and 1629.0 (1205–1815) BAU/mL, respectively. Of those IN-KTR in whom the primary vaccination failed, 46.67% (21/45) of patients achieved seroconversion after the third dose. No serious adverse events after the third dose were reported. In strata analyses, after the third dose, 66% (40/60) of patients vaccinated with BNT162b2 and 82.6% (19/23) of patients vaccinated with mRNA-1273 seroconverted with a median anti-s titer of 384.5 (144–837) BAU/mL and 1620 (671–2040) BAU/mL, respectively. Conclusions: The use of a third dose of mRNA vaccine may be of benefit for KTR, especially for those in whom the primary vaccination failed. Vaccines with a higher dose of mRNA and a longer interval between doses of the primary vaccination, such as mRNA-1273, seem to be the preparations of choice in immunocompromised individuals.

Introduction: Patients after SARS-CoV-2 infection frequently face “Post-COVID-19 Syndrome”, defined by symptoms that develop during or after COVID-19, continue for more than 12 weeks, and are not explained by an alternative diagnosis. We aimed to evaluate the presence of post-COVID-19 syndrome and its predictors in kidney transplant recipients (KTR) 6 months after the disease. Materials and Methods: A total of 67 KTR (38 m) with a mean age of 53.6 ± 14 years, 7.3 ± 6.4 years post-transplant were included in the cohort longitudinal study. Thirty-nine (58.2%) of them were hospitalized, but not one required invasive ventilation therapy. They were interviewed 6 months after being infected, with a series of standardized questionnaires: a self-reported symptoms questionnaire, the modified British Medical Research Council (mMRC) dyspnea scale, EQ-5D-5L questionnaire, and EQ-VAS scale. Results: Post-COVID-19 syndrome was diagnosed in 70.1% of KTR and 26.9% of them reported at least three persistent symptoms. The most common symptoms were fatigue (43.3%), hair loss (31.3%), memory impairment (11.9%), muscle aches, and headaches (11.9%). Dyspnea with an mMRC scale grade of at least 1 was reported by 34.3% patients vs. 14.9% before infection; 47.8% stated that they still feel worse than before the disease. Mean EQ-VAS scores were 64.83 vs. 73.34 before infection. The persistent symptoms are more frequent in older patients and those with greater comorbidity. Conclusions: Persistent symptoms of post-COVID-19 syndrome are present in the majority of KTR, which highlights the need for long-term follow-up as well as diagnostic and rehabilitation programs.

Vaccination against COVID-19 in patients with end-stage renal disease (ESRD) on replacement therapy and kidney transplant recipients (KTRs) is particularly important due to the high mortality rate. Here, we tested the local and systemic immunity to the novel Pfizer BioNTech (BNT162b2) messenger RNA (mRNA) in ESRD, KTR patients, and healthy individuals (150 subjects). The ESRD group was divided into: hemodialysis (HD) and peritoneal dialysis (PD). We investigated the local and systemic immunity based on anti-N (nucleoprotein) and anti-S (spike1/2) Immunoglobulin A (IgA) and Immunoglobulin G (IgG) antibodies, respectively. Additionally, we performed an Interferon gamma (IFN-γ) release test Interferon-gamma release assay (IGRA) to monitor the cellular component of vaccine response. The control group had the highest level of anti-S IgG antibodies (153/2,080 binding antibody units (BAU)/ml) among all analyzed patients after the 1st and 2nd dose, respectively. The HD group (48/926 BAU/ml) had a diminished antibody level compared to PD (93/1,607 BAU/ml). Moreover, the seroconversion rate after the 1st dose was lower in HD than PD (56% vs. 86%). KTRs had extremely low seroconversion (33%). IgA-mediated immunity was the most effective in the control group, while other patients had diminished IgA production. We observed a lower percentage of vaccine responders based on the IFN-γ level in all research participants (100% vs. 85% in control, 100% vs. 80% in PD, 97% vs. 64% in HD). 63% of seropositive KTRs had a positive IGRA, while 28% of seronegative patients produced IFN-γ. Collectively, PD patients had the strongest response among ESRD patients. Two doses of the Pfizer vaccine are ineffective, especially in HD and KTRs. A closer investigation of ESRD and KTRs is required to set the COVID-19 vaccine clinical guidance.Clinical Trial Registration Numberwww.ClinicalTrials.gov, identifier: NCT04 905 862

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