MO970: Humoral Response After Successive Doses of Mrna Vaccine Against Sars-Cov-2 in Stable Kidney Transplant Recipients

Abstract

BACKGROUND AND AIMSThe poor humoral response after vaccination against SARS-CoV-2 in kidney transplant (KT) patients led to the approval of a third dose. Recent data show an increase in the antibody titer, although lower than in the general population. Our aim is to analyze the humoral immune response after the third dose a mRNA vaccine against SARS-CoV-2 and the evolution of the antispike antibody (antiS) titers in KT recipients.METHODWe performed a prospective cohort study of stable KT patients from our center who received three doses of a mRNA vaccine from March to November 2021. KT recipients with less than 6 months after transplantation and with active oncological or hematologic disease were excluded. We determined antiS titers (Abbott SARS‐CoV‐2 IgG chemiluminescent microparticle immunoassay) at baseline, one month after the second dose and one month after the third one. We compared those KT patients who seroconverted with 2 and with 3 doses of vaccine and those who did not seroconvert. To identify risk factors for no seroconversion, a logistic regression analysis was carried out.RESULTSWe included 83 KT. Mean age was 59.3 years and 62.7% were male. The median time from KT to the first vaccine dose was 94 months and between the second and third dose median time was 4 months. Seroconversion rate was 63.8% after 2 doses and 85.5% after the third one (P < 0.001). Twelve KT did not develop antibodies (Table 1). Patients who did not seroconvert were older (P = 0.047), had a worse renal function (P = 0.009) and had fewer lymphocytes than those that developed antibodies (0.013). Besides, they almost half of them received a KT from a non-heart-beating donor (P = 0.026) and were treated with thymoglobulin in the 2 years prior to the vaccine more frequently (P = 0.007). In patients who seroconverted after 2 doses, we observed a 10-fold increase in the antiS titer after the third vaccine (82 [34–350] UI/mL versus 814 [205–2415] UI/mL; P < 0.001). No patients had neither acute rejection nor serious adverse effects. In the multivariable analysis advanced age, a worse kidney function and recent treatment with thymoglobulin were risk factors for no seroconversion (Table 1).CONCLUSIONThe third dose of a mRNA vaccine against SARS-CoV-2 significantly increased the seroconversion rate and the antiS titers in stable KT patients. Advanced age, poorer kidney function and immunosuppressive treatment are risk factors for no seroconversion.