Immunogenicity and Reactogenicity After SARS-CoV-2 mRNA Vaccination in Kidney Transplant Recipients Taking Belatacept.

BACKGROUND: Belatacept may impair humoral immunity, impacting the effectiveness of SARS-CoV-2 mRNA vaccines in transplant recipients. We investigated immunogenicity after SARS-CoV-2 mRNA vaccines in kidney transplant recipients who are and are not taking belatacept. METHODS: Participants were recruited between 12/9/2020 - 4/1/2021. Blood samples were collected after dose 1 and dose 2 (D1, D2), and analyzed using either an anti-SARS-CoV-2 enzyme immunoassay against the S1 domain of the SARS-CoV-2 spike protein or immunoassay against the receptor-binding domain of the SARS-CoV-2 spike protein. Stabilized inverse probability of treatment weights (IPTW) was used to compare immunogenicity and a weighted logistics regression was used to calculate fold change of positive response. RESULTS: Among the 609 participants studied, 24 (4%) were taking belatacept. After dose 1, 0/24 (0%) belatacept patients had detectable antibodies, compared to 77/568 (14%) among the equivalent nonbelatacept population (p=0.06). After dose 2, 1/19 (5%) belatacept patients had detectable antibodies, compared to 190/381 (50%) among the equivalent nonbelatacept population (p<0.001). Belatacept use was associated with 16.7-fold lower odds of having a positive post-D2 titer result (p <0.01). CONCLUSIONS: Additional measures need to be explored in order to protect kidney transplant recipients taking belatacept. Best safety practices should be continued despite vaccination among this population.