TOPLINE:

Among allogeneic hematopoietic cell transplant recipients, the use of sirolimus for graft-vs-host disease (GVHD) prophylaxis was linked to a higher risk for respiratory syncytial virus (RSV) infection, whereas higher serum neutralizing antibody levels were linked to a lower risk within the first 100 days post-transplant.

METHODOLOGY:

• Researchers analyzed 471 allogeneic hematopoietic cell transplant recipients (mean age, 46 years; 64% men) who underwent transplant in 2005-2010 and were followed to identify clinical and humoral immune factors associated with the risk for RSV infection until the first 100 days post-transplant.
• Recipients completed weekly symptom and exposure surveys and provided weekly samples of nasal washes and serum for up to 1 year of post-transplant.
• RSV in nasal washes was detected using multiplex polymerase chain reaction (PCR); serum neutralization assays measured neutralizing antibody levels to RSV before and after transplant.
• Analyses included recipients with PCR-confirmed RSV infection and control recipients whose serum was collected through follow-up and no RSV was detected.
• The outcome was the first RSV detection by PCR within 100 days post-transplant.

TAKEAWAY:

• Overall, 3.4% of recipients had RSV detected within 100 days post-transplant; the median time to the first detection was 37.5 days.
• Use of sirolimus for GVHD prophylaxis was associated with an increased risk for RSV infection after adjustment for age and transplant year (hazard ratio [HR], 7.3; 95% CI, 2.2-24.3).
• Recipients with higher serum neutralizing antibody had significantly lower risk for RSV infection; each 10-fold increase in levels was associated with a 39% reduction in risk (HR, 0.61; 95% CI, 0.42-0.94).
• Among the 16 participants with RSV infection, 25% were hospitalized, 19% had lower respiratory tract involvement, and 25% received ribavirin; no RSV-related deaths occurred within 100 days post-transplant.

IN PRACTICE:

“The demonstration of serum neutralizing antibody levels as an inverse correlate of risk in this present study has implications for enabling clinical trials and immunobridging studies of vaccines and mAbs [monoclonal antibodies] in HCT [hematopoietic cell transplant] recipients and other immunocompromised populations,” the authors wrote.

SOURCE:

This study was led by Sara Pernikoff, Fred Hutchinson Cancer Center, Seattle. It was published online on January 20, 2026, in Open Forum Infectious Diseases.

LIMITATIONS:

This study had a small sample size. Findings from recipients who underwent transplantation in 2005-2010 may not apply to current recipients as clinical practices have evolved over time. Additionally, antibody assays for participants with RSV infection and control participants were conducted separately.

DISCLOSURES:

This study was supported by multiple sources, including a New Investigator Award from the American Society for Transplantation and Cellular Therapy, the Amy Strelzer Manasevit Award from the National Marrow Donor Program, and grants from the National Institute of Allergy and Infectious Diseases. Several authors disclosed receiving research support and consulting fees from various pharmaceutical companies. One author was an inventor on patents related to RSV antibodies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.