RESUMEN
PURPOSE: Advanced age is associated with an impaired humoral immune response to SARS-CoV-2 mRNA vaccination in kidney transplant recipients (KTR). The mechanisms are, however, poorly understood. Frailty syndrome assessment may determine the most vulnerable population. METHODS: This study is a secondary analysis of a prospective study (NCT04832841) regarding seroconversion after BNT162b2 vaccination, including 101 SARS-CoV-2 naïve KTR 70 years and older. The Fried frailty components were evaluated, and antibodies against S1 and S2 subunits of SARS-CoV-2 were examined > 14 days after the second dose of BNT162b2 vaccine. RESULTS: Seroconversion was observed in 33 KTR. Male gender, eGFR, MMF-free immunosuppression, and a lower frailty score were associated with higher seroconversion rates in univariable regression. Concerning frailty components, physical inactivity had the most negative effect on seroconversion (OR = 0.36, 95% CI 0.14-0.95, p = 0.039). In a multivariable regression adjusted for eGFR, MMF-free immunosuppression, time from transplant and gender, pre-frail (OR = 0.27, 95% CI 0.07-1.00, p = 0.050), and frail status (OR = 0.14, 95% CI 0.03-0.73, p = 0.019) were associated with an increased risk of unresponsiveness to SARS-CoV-2 vaccines. CONCLUSION: Frailty was associated with an impaired humoral response to SARS-CoV-2 mRNA vaccination in older SARS-CoV-2 naïve KTR. TRAIL REGISTRATION: This study is registered under the identifier NCT04832841 on ClinicalTrials.gov.