RSV vaccination in immunocompromised adults

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract disease in immunocompromised adults, including solid organ and hematopoietic stem cell transplant recipients. Following the 2023 licensure of three RSV vaccines for older adults, increasing numbers of immunocompromised individuals have become eligible for vaccination, although these populations were largely excluded from pivotal phase 3 trials.

We synthesize emerging data from prospective immunogenicity studies and large real-world effectiveness analyses evaluating RSV vaccines in immunocompromised adults.

Humoral immune responses are attenuated and heterogeneous, with seroconversion rates commonly ranging from 30-60% in transplant populations and strongly influenced by time since transplantation, lymphocyte counts, and exposure to antimetabolites such as mycophenolate. Despite reduced antibody responses, first-season vaccine effectiveness against hospitalization is generally between 65% and 75% in immunocompromised adults. Two-season analyses demonstrate waning protection, more pronounced than in immunocompetent individuals. Cellular immune responses, particularly CD4 T-cell responses, may be preserved despite diminished serologic responses, suggesting that antibody measurements alone may underestimate clinical protection.

Although immunogenicity is reduced and durability shorter than in immunocompetent adults, RSV vaccination provides meaningful protection against severe disease. Optimization of vaccination timing, booster strategies, and integration of passive immunization approaches warrant further study in high-risk subgroups.