This clinical trial is focused on studying the effects of vaccines for the Respiratory Syncytial Virus (RSV) in patients who have undergone allogeneic hematopoietic stem cell transplantation. This type of transplantation involves using stem cells from a donor to replace damaged or diseased bone marrow. The study will test two different vaccines: Arexvy and Abrysvo. Arexvy is a vaccine that contains a part of the RSV virus called the glycoprotein F, which is stabilized in a specific form and combined with an ingredient to boost the immune response. Abrysvo is a bivalent vaccine, meaning it targets two subgroups of the RSV virus, using stabilized proteins from each subgroup.
The purpose of the study is to evaluate how well these vaccines work in helping the immune system of transplant recipients respond to RSV. Participants will be randomly assigned to receive either the Arexvy or Abrysvo vaccine. The study will monitor the participants’ immune response to the vaccine, specifically looking for a significant increase in antibodies, which are proteins the body makes to fight infections. The study will also include a group of healthy older adults to compare their immune responses to those of the transplant recipients.
Participants will receive the vaccine through an intramuscular injection, which means it will be given as a shot into a muscle. The study will take place over several months, with participants receiving one or two doses of the vaccine, depending on their initial response. The goal is to understand how effective the vaccines are in preventing RSV infections in people who have had a stem cell transplant and to identify any patterns in the immune response that could predict how well someone might respond to the vaccine.



Belgium