Safety and Immunogenicity of Vaccines in Children with Kaposiform Hemangioendothelioma Receiving Sirolimus: A Prospective Study.

Abstract

Background: Sirolimus is an effective treatment for kaposiform hemangioendothelioma (KHE), a rare vascular tumor in children. However, its immunosuppressive properties raise concerns regarding the safety and efficacy of vaccinations during treatment. This study aims to evaluate the safety and immunogenicity of inactivated and live-attenuated vaccines administered to pediatric KHE patients undergoing sirolimus therapy.

Methods: We conducted a prospective study involving 56 KHE children receiving sirolimus who were vaccinated during treatment. Data on vaccine-related adverse events were collected to assess safety. Immunogenicity was evaluated by measuring seroconversion or protective antibody titers against vaccines, including Hepatitis B, DTaP, and MMR.

Results: Among 56 catch-up vaccinated children, no serious adverse events related to vaccination were observed. Mild local or systemic reactions occurred in a minority of patients. Serological analysis demonstrated that children with kaposiform hemangioendothelioma (KHE) receiving sirolimus therapy were able to generate and sustain robust protective antibody responses following vaccination. High seroconversion rates and antibody titers were observed for both inactivated vaccines (e.g., hepatitis B and DTaP) and live-attenuated vaccines (e.g., MMR). Protective antibody levels were maintained both within 3 months and beyond 6 months post-vaccination, indicating durable immunogenicity under sirolimus treatment.

Conclusions: Vaccination during sirolimus therapy appears to be safe and immunogenic in children with KHE. These findings support the administration of both inactivated and live-attenuated vaccines under appropriate clinical monitoring in this rare patient population.