Reactogenicity and Immunogenicity of Adjuvanted and Nonadjuvanted RSV Vaccines in Solid Organ Transplant Recipients

Solid organ transplant (SOT) recipients are at high risk for severe respiratory syncytial virus (RSV). While RSV vaccine immunogenicity data in transplant populations are emerging, questions remain regarding the magnitude and durability of responses, cellular immunity, and determinants of decreased response.

We conducted a prospective, single-center cohort study evaluating RSV vaccine reactogenicity and immunogenicity in SOT recipients compared with healthy controls. Serum was collected pre-vaccination and at 1, 3, and 6 mo post-vaccine to measure anti-fusion glycoprotein antibodies to RSV A and B and anti-nucleocapsid antibodies as a marker of natural infection. Peripheral blood mononuclear cells were collected from a subset for RSV-fusion (F)-specific cellular analyses.

Forty-three SOT recipients (median age, 65) and 16 controls were enrolled (from October 2023 to January 2024). Mild reactogenicity occurred in ~25% of participants, with no severe events. In SOT recipients, anti-fusion glycoprotein IgG, RSV-F-specific CD4⁺ and CD8⁺ T cells increased significantly at 1 mo (P < 0.01), with similar antibody fold changes to controls. Antibody responses remained durable through 6 mo; the rate of decline did not differ significantly between groups. Mycophenolate use was inversely correlated with antibody titers (P < 0.05); vaccine type, organ, and time from transplant were not. The adjuvanted vaccine induced greater RSV-F-specific CD4⁺ T-cell responses at 3 mo. One SOT recipient developed RSV during the study.

RSV vaccination was well tolerated and immunogenic in SOT recipients. Further research should optimize vaccination strategies and ideal timing for booster doses.