Peer-reviewed article

Antibody levels and immune memory in children with kaposiform hemangioendothelioma treated with sirolimus after catch up vaccination.

Junhong Yuan, Yingjing Ding, Zuopeng Wang, Liyun Su, Kai Li · 19 May 2026

Abstract

This study evaluated the safety, immunogenicity, and post-vaccination immune responses of timely, sequential catch-up vaccination in children with Kaposiform hemangioendothelioma (KHE) undergoing sirolimus treatment. From July 2020 to November 2021, sixteen children with KHE receiving sirolimus in sustained remission were enrolled, along with 15 age-matched healthy children as controls. Patients in the sirolimus-treated group underwent immune assessment prior to receiving catch-up vaccinations, including Hepatitis B, Measles-Mumps-Rubella (MMR), Epidemic Encephalitis B, and meningococcal vaccines. Demographic characteristics, clinical outcomes, immune cell profiles, viral antibody indices, and post-vaccination adverse events were systematically recorded. Vaccination was well tolerated in sirolimus-treated children, with only one case of transient low-grade fever and tonsillitis reported. Seroprotective antibody responses to both live-attenuated and inactivated vaccines were comparable between the sirolimus-treated group and healthy controls. Notably, the proportion of IgG+ memory B cells was significantly higher in the case group than in controls (57.33% ± 13.48% vs. 47.33% ± 12.13%, P = .039). In addition, immune cell subset distributions and post-vaccination cytokine response trajectories were similar between the two groups, indicating preserved vaccine-induced immune competence. Collectively, these findings demonstrate that catch-up vaccination is safe, immunogenic, and well tolerated in children with KHE receiving sirolimus therapy, supporting the feasibility of timely immunization in this immunocompromised pediatric population.